unimelb-econ10004-microeconomics

0）先把“考试规则 + 试卷长相”记死（这决定复习策略）

• Final 的性质
  • 权重：50%，并且是 hurdle：final 本身必须 ≥50% 才能通过本课。[1]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfThis is not lecture notes. It is a complete, self-contained course in every model ECON10004 tests - every curve drawn, every result derived - written so the same pages serve you three times across the semester. 这不是课堂笔记,而是一套完整、自成体系的课程,涵盖ECON10004 考查的每个模型 -- 每条曲线都画出来、每个结论都 推导出来 -- 其编排让同一批内容能在整个学期里为你服务三次。 A 1 . LEARN 1·学习 You haven't watched the lecture. Read a chapter top to bottom. Every concept opens with plain-English intuition and a labelled diagram, then a worked example with real numbers. You can learn the model here cold. 你还没看过这节课。把一章从头 读到尾。每个概念都先用大白话 直觉加带标注的图开篇,再配一 个用真实数字的例题。你完全能 在这里把模型从零学会。 B 2 . REVISE 2 · 复习 You've done the lecture and tutorial. Re-draw each diagram from memory, then work the practice bank with solutions covered. The "exam move" boxes show the steps markers reward. 你已上过课、做过习题课。凭记 忆重画每幅图,然后盖住答案做 练习题库。“考试招式”框展示了 阅卷人会给分的步骤。 C 3 . EXAM 考试 It's SWOTVAC. The recap strip at the head of each chapter is your map. The blueprint overleaf shows where the marks sit - and why the final exam decides whether you pass at all. 已经到 SWOTVAC (考前复习 周)了。每章开头的回顾条就是 你的地图。后页的蓝图标出分值 落在哪 -- 以及为什么期末考试 (final exam) 直接决定你能否 通过。 ! Read this before anything else: the exam is a HURDLE 先读这条:考试是一道及格线(HURDLE) ECON10004's final exam is worth 50% of your subject mark - and it is a hurdle: you must score at least 50% on the final exam itself to pass the subject, no matter how good your quizzes, assignment and tutorial marks are. Perfect continuous assessment will not save a failed exam. This book exists to get you over that hurdle with room to spare. ECON10004 的期末考试占科目总分的 50% -- 而且它是一道及格线(hurdle):无论你的测验、作业和习题课成绩多 好,期末考试本身必须至少拿到50% 才能通过本科目。再完美的平时成绩也救不了一场不及格的考试。本书的存在就 是为了让你稳稳跨过这道及格线、并留有余地。 AskSia Library · ECON10004 · 双语 Bilingual i How this book was built 这本书是怎么做出来的 Every model, diagram and worked number here is grounded in this subject's own materials: the lecture slides, weekly tutorial questions, pre-tutorial quizzes and the exam-revision sessions (with worked solutions). Numbers in worked examples are the subject's own. Verify against your Canvas before the exam - details can shift between cohorts. 本书中每个模型、每幅图、每个例题数字都扎根于本科目自己的材料:讲义幻灯片、每周习题课题目、课前测验,以及 考试复习课(含标准解答)。例题中的数字均为本科目自有。考前请对照你的 Canvas 核验 -- 细节可能随届次变动。 - AskSia Library · ECON10004 · 双语 Bilingual THE BLUEPRINT - THE EXAM BLUEPRINT EXAM . 50% + HURDLE Where every mark lives 每一分都在哪里[4]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfAnd why the final exam is the one that decides everything 为何期末考试决定一切 Your subject mark is built from four pieces - but they are not equal. The final exam is half your grade and a hurdle you must clear to pass at all. 你的科目成绩由四部分构成 -- 但它们并不等重。期末考试(final exam)占你成绩的一半,而且是你必须达到才能及格的及 格线 (hurdle)。 50% FINAL EXAM 期末考试 ≥50% HURDLE TO PASS 及格线 2 hrs EXAM LENGTH 考试时长 12 topics ALL EXAMINABLE 全部可考 The four assessment pieces 四项考核 Component Weight When Final examination - hurdle 50% Exam period Mid-semester test 25% Wk 4-7 Individual written assignment 15% Wk 7-10 Tutorial attendance & participation 10% Weekly Continuous marks come from weekly engagement: the best 9 of 11 pre-tutorial (FLUX) quizzes and attendance at 10 of 12 tutorials. Useful marks - but they cannot rescue a failed exam. 平时分来自每周的参与:11次课前 (FLUX) 测验中取最好 的9次,以及12次习题课(tutorial)中出席10次。这些分有 用 -- 但救不了一场不及格的考试。 What the exam looks like 考试长什么样
  • 时长：2 小时。[4]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfAnd why the final exam is the one that decides everything 为何期末考试决定一切 Your subject mark is built from four pieces - but they are not equal. The final exam is half your grade and a hurdle you must clear to pass at all. 你的科目成绩由四部分构成 -- 但它们并不等重。期末考试(final exam)占你成绩的一半,而且是你必须达到才能及格的及 格线 (hurdle)。 50% FINAL EXAM 期末考试 ≥50% HURDLE TO PASS 及格线 2 hrs EXAM LENGTH 考试时长 12 topics ALL EXAMINABLE 全部可考 The four assessment pieces 四项考核 Component Weight When Final examination - hurdle 50% Exam period Mid-semester test 25% Wk 4-7 Individual written assignment 15% Wk 7-10 Tutorial attendance & participation 10% Weekly Continuous marks come from weekly engagement: the best 9 of 11 pre-tutorial (FLUX) quizzes and attendance at 10 of 12 tutorials. Useful marks - but they cannot rescue a failed exam. 平时分来自每周的参与:11次课前 (FLUX) 测验中取最好 的9次,以及12次习题课(tutorial)中出席10次。这些分有 用 -- 但救不了一场不及格的考试。 What the exam looks like 考试长什么样
  • 12 个 topic 都可考（整门课都在考纲内）。[4]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfAnd why the final exam is the one that decides everything 为何期末考试决定一切 Your subject mark is built from four pieces - but they are not equal. The final exam is half your grade and a hurdle you must clear to pass at all. 你的科目成绩由四部分构成 -- 但它们并不等重。期末考试(final exam)占你成绩的一半,而且是你必须达到才能及格的及 格线 (hurdle)。 50% FINAL EXAM 期末考试 ≥50% HURDLE TO PASS 及格线 2 hrs EXAM LENGTH 考试时长 12 topics ALL EXAMINABLE 全部可考 The four assessment pieces 四项考核 Component Weight When Final examination - hurdle 50% Exam period Mid-semester test 25% Wk 4-7 Individual written assignment 15% Wk 7-10 Tutorial attendance & participation 10% Weekly Continuous marks come from weekly engagement: the best 9 of 11 pre-tutorial (FLUX) quizzes and attendance at 10 of 12 tutorials. Useful marks - but they cannot rescue a failed exam. 平时分来自每周的参与:11次课前 (FLUX) 测验中取最好 的9次,以及12次习题课(tutorial)中出席10次。这些分有 用 -- 但救不了一场不及格的考试。 What the exam looks like 考试长什么样
• 评分结构（你该怎么拿分）
  • 题型大致一半是：选择题（definitions & diagrams）
  • 另一半是：多问计算 + 简答
  • 画图（标 CS/PS/DWL 阴影）贯穿全卷。[5]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfFormat Share Multiple choice (definitions & diagrams) ~half Multi-part calculation & short answer ~half Graph-drawing (shade CS/PS/DWL) throughout ✓ The strategy this dictates 由此定下的策略 The whole subject is examinable, but it is procedural: a handful of models - supply & demand, surplus, policy & deadweight loss, costs, competition, monopoly, externalities - applied to fresh numbers and drawn as graphs. The recurring calculation is one chain: find equilibrium - elasticity - surplus - impose a policy - deadweight loss. Master that chain and the graphs, and the exam can't surprise you. This book is ordered to build exactly that. 整门科目都可能考,但它是程式化的:一小撮模型 -- 供求、剩余、政策与无谓损失、成本、竞争、垄 断、外部性 -- 套用新数字并画成图。反复出现的计 算就是一条链:求均衡→弹性→剩余→施加政策 →无谓损失。掌握这条链和那些图,考试就难不倒 你。本书正是按这一目标编排的。 AskSia Library · ECON10004 · 双语 Bilingual CONTENTS - CONTENTS The whole subject, in one ordered book 整门课,一本有序的书 Twelve lecture topics - one exam-ready map 十二讲主题→一张考前地图 Ch Topic Core idea Part 1 . The market model 1 The economic way of thinking scarcity . trade-offs → 2 Demand & supply the core model → 3 Elasticity responsiveness · revenue → 4 Surplus & market efficiency CS . PS . the invisible hand →
• 最重要结论（复习抓手）
  • 这门课“很程式化”：核心就是少数模型（供需、剩余、政策与DWL、成本与竞争、垄断、外部性等）反复换数字、换情境、换问法。[5]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfFormat Share Multiple choice (definitions & diagrams) ~half Multi-part calculation & short answer ~half Graph-drawing (shade CS/PS/DWL) throughout ✓ The strategy this dictates 由此定下的策略 The whole subject is examinable, but it is procedural: a handful of models - supply & demand, surplus, policy & deadweight loss, costs, competition, monopoly, externalities - applied to fresh numbers and drawn as graphs. The recurring calculation is one chain: find equilibrium - elasticity - surplus - impose a policy - deadweight loss. Master that chain and the graphs, and the exam can't surprise you. This book is ordered to build exactly that. 整门科目都可能考,但它是程式化的:一小撮模型 -- 供求、剩余、政策与无谓损失、成本、竞争、垄 断、外部性 -- 套用新数字并画成图。反复出现的计 算就是一条链:求均衡→弹性→剩余→施加政策 →无谓损失。掌握这条链和那些图,考试就难不倒 你。本书正是按这一目标编排的。 AskSia Library · ECON10004 · 双语 Bilingual CONTENTS - CONTENTS The whole subject, in one ordered book 整门课,一本有序的书 Twelve lecture topics - one exam-ready map 十二讲主题→一张考前地图 Ch Topic Core idea Part 1 . The market model 1 The economic way of thinking scarcity . trade-offs → 2 Demand & supply the core model → 3 Elasticity responsiveness · revenue → 4 Surplus & market efficiency CS . PS . the invisible hand →

1）考前最该死磕的“万能五连链条”（本课最高频计算骨架）

• 书里把它称为signature chain / calculation chain，几乎所有大题都在重复这一套：
  • (1) 均衡：设 $Q_d=Q_s$ 求 $P^*,Q^*$
  • (2) 弹性：点弹性公式
  • (3) 剩余：$CS,PS$ 三角形面积
  • (4) 上政策（税/补贴/管制/关税…）：产生 wedge 或改变交易量
  • (5) 算无谓损失：$DWL$ 三角形
  • 并且要对账：$CS+PS+\text{revenue}+DWL$ 要能“加回去”对上总剩余。[2]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf重复博弈与合作 If the game is played once, defection wins and cooperation is doomed. But oligopolists meet repeatedly. With an indefinite horizon, a firm can sustain the cooperative price by threatening to punish a cheater - for example, matching any price cut forever after. If the long-run loss from triggering that price war exceeds the one-off gain from cheating, cooperation can hold. This is how some collusion survives in practice, and why competition law watches repeated-interaction industries closely. 若博弈只玩一次,背叛取胜,合作注定失败。但寡头之间反 复相遇。在无限期视角下,企业可以靠威胁惩罚作弊者来维 持合作价 -- 例如从此永远跟降。若触发价格战的长期损失 超过作弊的一次性收益,合作就能维持。这就是现实中部分 合谋得以存续的原因,也是竞争法密切关注反复互动行业的 原因。 AskSia Library · ECON10004 · 双语 Bilingual i Recap - Chapter 12 in six lines 回顾 -- 第12章六行速记 (1) Game theory handles strategic settings (oligopoly) where your payoff depends on others' choices. (2) Read the payoff matrix: row payoff first, column second. (3) A dominant strategy is best regardless of the rival; play it. (4) A Nash equilibrium is where each best-responds - no one deviates alone (stable, not necessarily efficient). (5) The prisoner's dilemma: individually rational - collectively bad; both confess / both compete. (6) Cartels are unstable - each member gains by cheating; only repeated play with credible punishment can sustain cooperation. (1) 博弈论处理策略性情境(寡头),你的收益取决于他人的选择。(2)读收益矩阵:行收益在前,列收益在后。(3)占优 策略是无论对手怎样都最优的;打它。(4)纳什均衡是各自做最优反应 -- 没人单独偏离(稳定,未必有效)。(5)囚徒困 境:个体理性→集体糟糕;双双认罪/双双竞争。(6)卡特尔不稳定 -- 每个成员靠作弊获益;只有带可信惩罚的反复博 弈才能维持合作。 AskSia Library · ECON10004 · 双语 Bilingual CH 13 . PRACTICE P1 - CHAPTER 13 . PRACTICE BANK DRILL TO EXAM STANDARD Drill the exam, with full solutions 刷考题,附完整解答 Six graded problems in the real review-session style - worked end to end 六道分级题,真实复习课风格 -- 全程解答 These are exam-style problems, built on the real review-session and tutorial templates: multi-part calculation, a graph to draw, and a MCQ set. Every number is verified against this subject's own worked solutions. Treat each one as the real thing first; read the worked answer second. 这些是考试题型的习题,依据真实的复习课与习题课模板编排:多问计算、需作图的题、以及一组选择题。每个数字都已对照 本科目自己的标准解答核验。请先把每道题当作真考来做,之后再看解析。 - ★ How to use this bank 如何使用这个题库 Cover the solution. Work each problem on paper before you read a single line of the answer - recognition is not recall. Budget ~1 minute per mark. A 15-mark problem is a 15-minute problem; if you stall, move on and return. Always draw and fully label the graph - axes, both curves, equilibrium, and the shaded CS / PS / DWL. Graph marks are the easiest marks in the paper. Reconcile at the end: CS + PS + revenue + DWL must add back to the original total surplus, every time. 盖住答案。读到答案的任何一行之前,先在纸上把每 道题做出来 -- 认得出不等于答得出。每分预算约1 分钟。一道15分的题就是15 分钟的题;卡住了就跳 过、稍后回来。永远画出并完整标注图形 -- 坐标 轴、两条曲线、均衡点,以及涂好阴影的 CS/ PS / DWL。图形分是全卷最容易拿的分。最后做对账:CS + PS+ 收入 + DWL 每次都必须加回到原始的社会总 剩余。 ✓ The one chain behind most of it 贯穿大部分内容的那条链 Five of the six calculation patterns are the same move in disguise: set Qd = Qs for P*, Q* - point elasticity + CS / PS as triangles - impose a policy - deadweight loss. Learn it once on P1 and you can re- run it on a tax, a floor, an externality or a monopoly with the numbers swapped. 六种计算套路里有五种是同一招的变装:令 Qd =Qs 求 P *、 Q*→ 点弹性 → CS/ PS 作为三角形→施 加政策→无谓损失。在第1页学会一次,就能换上数 字在税、价格下限、外部性或垄断上重跑一遍。 i Difficulty & marks shown on each card 每张卡片都标注难度与分值 Marks track the real review-session allocations (e. g. the signature chain is marked 3+3+3+3+3 = 15). Use them to pace yourself against the clock. 分值对应真实复习课的分配(例如标志性的链条按 3+3+3+3+3=15 计分)。用它来对着时钟掌握节奏。 AskSia Library · ECON10004 · 双语 Bilingual[5]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfFormat Share Multiple choice (definitions & diagrams) ~half Multi-part calculation & short answer ~half Graph-drawing (shade CS/PS/DWL) throughout ✓ The strategy this dictates 由此定下的策略 The whole subject is examinable, but it is procedural: a handful of models - supply & demand, surplus, policy & deadweight loss, costs, competition, monopoly, externalities - applied to fresh numbers and drawn as graphs. The recurring calculation is one chain: find equilibrium - elasticity - surplus - impose a policy - deadweight loss. Master that chain and the graphs, and the exam can't surprise you. This book is ordered to build exactly that. 整门科目都可能考,但它是程式化的:一小撮模型 -- 供求、剩余、政策与无谓损失、成本、竞争、垄 断、外部性 -- 套用新数字并画成图。反复出现的计 算就是一条链:求均衡→弹性→剩余→施加政策 →无谓损失。掌握这条链和那些图,考试就难不倒 你。本书正是按这一目标编排的。 AskSia Library · ECON10004 · 双语 Bilingual CONTENTS - CONTENTS The whole subject, in one ordered book 整门课,一本有序的书 Twelve lecture topics - one exam-ready map 十二讲主题→一张考前地图 Ch Topic Core idea Part 1 . The market model 1 The economic way of thinking scarcity . trade-offs → 2 Demand & supply the core model → 3 Elasticity responsiveness · revenue → 4 Surplus & market efficiency CS . PS . the invisible hand →[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
• 考场节奏（官方建议）
  • 每 1 分≈1 分钟；先做最擅长的、先把稳分存起来。[2]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf重复博弈与合作 If the game is played once, defection wins and cooperation is doomed. But oligopolists meet repeatedly. With an indefinite horizon, a firm can sustain the cooperative price by threatening to punish a cheater - for example, matching any price cut forever after. If the long-run loss from triggering that price war exceeds the one-off gain from cheating, cooperation can hold. This is how some collusion survives in practice, and why competition law watches repeated-interaction industries closely. 若博弈只玩一次,背叛取胜,合作注定失败。但寡头之间反 复相遇。在无限期视角下,企业可以靠威胁惩罚作弊者来维 持合作价 -- 例如从此永远跟降。若触发价格战的长期损失 超过作弊的一次性收益,合作就能维持。这就是现实中部分 合谋得以存续的原因,也是竞争法密切关注反复互动行业的 原因。 AskSia Library · ECON10004 · 双语 Bilingual i Recap - Chapter 12 in six lines 回顾 -- 第12章六行速记 (1) Game theory handles strategic settings (oligopoly) where your payoff depends on others' choices. (2) Read the payoff matrix: row payoff first, column second. (3) A dominant strategy is best regardless of the rival; play it. (4) A Nash equilibrium is where each best-responds - no one deviates alone (stable, not necessarily efficient). (5) The prisoner's dilemma: individually rational - collectively bad; both confess / both compete. (6) Cartels are unstable - each member gains by cheating; only repeated play with credible punishment can sustain cooperation. (1) 博弈论处理策略性情境(寡头),你的收益取决于他人的选择。(2)读收益矩阵:行收益在前,列收益在后。(3)占优 策略是无论对手怎样都最优的;打它。(4)纳什均衡是各自做最优反应 -- 没人单独偏离(稳定,未必有效)。(5)囚徒困 境:个体理性→集体糟糕;双双认罪/双双竞争。(6)卡特尔不稳定 -- 每个成员靠作弊获益;只有带可信惩罚的反复博 弈才能维持合作。 AskSia Library · ECON10004 · 双语 Bilingual CH 13 . PRACTICE P1 - CHAPTER 13 . PRACTICE BANK DRILL TO EXAM STANDARD Drill the exam, with full solutions 刷考题,附完整解答 Six graded problems in the real review-session style - worked end to end 六道分级题,真实复习课风格 -- 全程解答 These are exam-style problems, built on the real review-session and tutorial templates: multi-part calculation, a graph to draw, and a MCQ set. Every number is verified against this subject's own worked solutions. Treat each one as the real thing first; read the worked answer second. 这些是考试题型的习题,依据真实的复习课与习题课模板编排:多问计算、需作图的题、以及一组选择题。每个数字都已对照 本科目自己的标准解答核验。请先把每道题当作真考来做,之后再看解析。 - ★ How to use this bank 如何使用这个题库 Cover the solution. Work each problem on paper before you read a single line of the answer - recognition is not recall. Budget ~1 minute per mark. A 15-mark problem is a 15-minute problem; if you stall, move on and return. Always draw and fully label the graph - axes, both curves, equilibrium, and the shaded CS / PS / DWL. Graph marks are the easiest marks in the paper. Reconcile at the end: CS + PS + revenue + DWL must add back to the original total surplus, every time. 盖住答案。读到答案的任何一行之前,先在纸上把每 道题做出来 -- 认得出不等于答得出。每分预算约1 分钟。一道15分的题就是15 分钟的题;卡住了就跳 过、稍后回来。永远画出并完整标注图形 -- 坐标 轴、两条曲线、均衡点,以及涂好阴影的 CS/ PS / DWL。图形分是全卷最容易拿的分。最后做对账:CS + PS+ 收入 + DWL 每次都必须加回到原始的社会总 剩余。 ✓ The one chain behind most of it 贯穿大部分内容的那条链 Five of the six calculation patterns are the same move in disguise: set Qd = Qs for P*, Q* - point elasticity + CS / PS as triangles - impose a policy - deadweight loss. Learn it once on P1 and you can re- run it on a tax, a floor, an externality or a monopoly with the numbers swapped. 六种计算套路里有五种是同一招的变装:令 Qd =Qs 求 P *、 Q*→ 点弹性 → CS/ PS 作为三角形→施 加政策→无谓损失。在第1页学会一次,就能换上数 字在税、价格下限、外部性或垄断上重跑一遍。 i Difficulty & marks shown on each card 每张卡片都标注难度与分值 Marks track the real review-session allocations (e. g. the signature chain is marked 3+3+3+3+3 = 15). Use them to pace yourself against the clock. 分值对应真实复习课的分配(例如标志性的链条按 3+3+3+3+3=15 计分)。用它来对着时钟掌握节奏。 AskSia Library · ECON10004 · 双语 Bilingual[3]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf坐标轴命名,两条曲线都画,均衡点标出,CS/ PS / DWL 涂阴影并标注。图形分是全卷最容易拿的分,绝 不会因算术失误而丢。即便题目没明确要求,也要画 图。 ~1 min PER MARK - PACE IT 每分一速 · 把控节奏 1st DO YOUR STRONGEST TOPICS FIRST 先做你最拿手的题 50% EXAM IS A HURDLE TO PASS 考试是一道及格线 ▰ BANK GRAPH + DEFINITION MARKS FIRST 先攒下作图分与定义分 ! Pace and pick your order 把控节奏、选好做题顺序 Budget ~1 minute per mark and start with the topics you know cold - bank the certain marks before the clock pressure hits. If a calculation stalls, still draw the graph and state the rule: partial method earns partial marks. Remember the exam is 50% of your grade and a hurdle - secure the graph and definition marks first, then reach for the rest. 每分预算约1分钟,从你最有把握的主题开始 -- 在时间压力袭来前先把稳拿的分收入囊中。若计算卡住,仍要画图并 陈述法则:部分方法得部分分。记住考试占总成绩50% 且是及格线 -- 先拿稳图形分和定义分,再去攻其余的。 Set Qd = Qs. Find the wedge. Shade the triangle. Label everything. You have drilled this - walk in and do it. 令 Qd=Qs。找出税楔。给三角涂阴影。把一切都标注清楚。你已经反复演练过 -- 走进考场把它做出来。 EXAM MORNING . ECON10004 AskSia Library · ECON10004 · 双语 Bilingual AskSia Library A+ COURSE PLAYBOOK FACULTY OF BUSINESS & ECONOMICS SEMESTER 1 . 2026 THE COMPLETE EXAM BIBLE Introductory Microeconomics 微观经济学导论 ONE SUBJECT · EVERY GRAPH, EVERY MODEL, EVERY MARK. 一门课 · 每张图、每个模型、每一分都拿下 ECON10004 . UNIVERSITY OF MELBOURNE 中英双语版 · BILINGUAL EDITION 英文主讲,中文随行 一 考试要点与术语保留英文原词 Built from this subject's own lecture slides, tutorial questions, weekly quizzes and exam- revision sessions. Teaches each model from first principles, draws every diagram, then drills it to exam standard - because the final exam is 50% of your grade and a hurdle. For personal study Not affiliated with or endorsed by the University of Melbourne takedowns@asksia. ai PREFACE HOW TO USE THIS BOOK Three students, one book 三个学生,一本书 Wherever you are right now, start here 无论你现在在哪,从这里开始
  • 卡住计算也别停：先画图 + 写规则，照样能拿到“方法分/作图分”。[3]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf坐标轴命名,两条曲线都画,均衡点标出,CS/ PS / DWL 涂阴影并标注。图形分是全卷最容易拿的分,绝 不会因算术失误而丢。即便题目没明确要求,也要画 图。 ~1 min PER MARK - PACE IT 每分一速 · 把控节奏 1st DO YOUR STRONGEST TOPICS FIRST 先做你最拿手的题 50% EXAM IS A HURDLE TO PASS 考试是一道及格线 ▰ BANK GRAPH + DEFINITION MARKS FIRST 先攒下作图分与定义分 ! Pace and pick your order 把控节奏、选好做题顺序 Budget ~1 minute per mark and start with the topics you know cold - bank the certain marks before the clock pressure hits. If a calculation stalls, still draw the graph and state the rule: partial method earns partial marks. Remember the exam is 50% of your grade and a hurdle - secure the graph and definition marks first, then reach for the rest. 每分预算约1分钟,从你最有把握的主题开始 -- 在时间压力袭来前先把稳拿的分收入囊中。若计算卡住,仍要画图并 陈述法则:部分方法得部分分。记住考试占总成绩50% 且是及格线 -- 先拿稳图形分和定义分,再去攻其余的。 Set Qd = Qs. Find the wedge. Shade the triangle. Label everything. You have drilled this - walk in and do it. 令 Qd=Qs。找出税楔。给三角涂阴影。把一切都标注清楚。你已经反复演练过 -- 走进考场把它做出来。 EXAM MORNING . ECON10004 AskSia Library · ECON10004 · 双语 Bilingual AskSia Library A+ COURSE PLAYBOOK FACULTY OF BUSINESS & ECONOMICS SEMESTER 1 . 2026 THE COMPLETE EXAM BIBLE Introductory Microeconomics 微观经济学导论 ONE SUBJECT · EVERY GRAPH, EVERY MODEL, EVERY MARK. 一门课 · 每张图、每个模型、每一分都拿下 ECON10004 . UNIVERSITY OF MELBOURNE 中英双语版 · BILINGUAL EDITION 英文主讲,中文随行 一 考试要点与术语保留英文原词 Built from this subject's own lecture slides, tutorial questions, weekly quizzes and exam- revision sessions. Teaches each model from first principles, draws every diagram, then drills it to exam standard - because the final exam is 50% of your grade and a hurdle. For personal study Not affiliated with or endorsed by the University of Melbourne takedowns@asksia. ai PREFACE HOW TO USE THIS BOOK Three students, one book 三个学生,一本书 Wherever you are right now, start here 无论你现在在哪,从这里开始

2）必背公式包（你按这几条背，覆盖半张卷）

• 2.1 均衡（所有计算的起点）

  • 核心操作：设 $Q_d=Q_s$（注意：令数量相等，不是令价格相等）。[10]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf例题市场:Qs=2P 与 Qq=100-2P 相交于 P *= $25, Q *= 50。同一幅图支撑着后面每一次剩余与政策计算。 i Reading the equations as a picture 把方程读成一幅图 Qd=100-2P hits the price axis at P=$50 (where Q=0) and the quantity axis at Q=100 (where P=0). Qs=2P starts at the origin. Sketching those intercepts before solving catches sign errors. Qd=100-2P 与价格轴交于 P=$50(此时 Q=0),与 数量轴交于 Q=100(此时 P=0)。Qs=2P 从原点出 发。求解前先画出这些截距能抓住符号错误。 ! Demand vs quantity demanded; P-on-axis confusion 需求 vs 需求量;P 在轴上的混淆 Two recurring slips: (1) Although we write Q as a function of P, economists draw P on the vertical axis - do the algebra in whichever form is given, then map to the graph. (2) Set quantities equal, never prices - demand and supply share the same market price, so it is Qd = Qs that pins down P *. 两个常犯的失误:(1)虽然我们把 Q 写成 P 的函数,经济学家却把 P 画在纵轴 -- 用给定的形式做代数,再映射到图 上。(2)令数量相等,绝不令价格相等 -- 供求共用同一市场价格,所以是 Qd= Qs 锁定 P *。 AskSia Library · ECON10004 · 双语 Bilingual ★ Exam move - the equilibrium-first habit 考试技巧 -- 先求均衡的习惯 Whatever the policy to come - tax, subsidy, floor, quota, tariff - the first marks are always the free-market equilibrium: set Qd=Qs, get (P*, Q*), and label it on a clean diagram. Everything in Chapters 4-6 is measured as a change from this point. 无论接下来是什么政策 -- 税、补贴、价格下限、配额、关税 -- 头几分总是自由市场均衡:令 Qd=Qs,求出(P*, Q*),并在干净的图上标出它。第4-6章的一切都以与该点的变化来度量。 AskSia Library · ECON10004 · 双语 Bilingual CH 3 . PED EXAM CALC STAPLE - CHAPTER 3 Elasticity 弹性 How much quantity responds - and the formula the exam expects 数量反应多大 -- 考试要的公式 A demand curve tells you quantity falls when price rises. Elasticity tells you by how much - it turns the slope into a unit-free number you can compute, compare and link to revenue. This is a calculation staple: the course uses the point formula, taken as an absolute value, every time. 需求曲线告诉你价格上升时数量下降。弹性(elasticity)告诉你下降多少 -- 它把斜率变成一个无量纲、可计算、可比较、 可与收益挂钩的数字。这是计算常客:本课程每次都用点弹性公式,并取绝对值。 ★ What the exam asks here 这里考试问什么 Compute the point elasticity & = (dQ/dP)(P/Q) at a stated price; classify it as elastic / inelastic / unit-elastic; apply the total-revenue rule to say which way to move price to raise revenue; and identify income and cross-price elasticities by sign. Numeric-entry questions want a clean number such as & = - 1 or -3. 在给定价格处计算点弹性 &=(dQ/dP)(P/Q);将其分类为富有弹性/缺乏弹性/单位弹性;运用总收益法则说出价格往哪 边调能提高收益;并按符号辨认收入弹性与交叉价格弹性。填空题要的是 c =- 1 或-3 这类干净数字。 3. 1 Price elasticity of demand 3. 1 需求价格弹性 (PED) The price elasticity of demand (PED) is the percentage change in quantity demanded divided by the percentage change in price - the responsiveness of quantity to price. 需求价格弹性(PED) (price elasticity of demand) 是需求量的百分比变化除以价格的百分比变化––衡量数量对价格的反 应程度。 PRICE ELASTICITY OF DEMAND
  • 常见失误
    • 把“需求 demand”和“需求量 quantity demanded”混了；
    • 因为代数写 $Q(P)$，但图上经济学把 $P$ 画在纵轴，所以容易映射错。[10]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf例题市场:Qs=2P 与 Qq=100-2P 相交于 P *= $25, Q *= 50。同一幅图支撑着后面每一次剩余与政策计算。 i Reading the equations as a picture 把方程读成一幅图 Qd=100-2P hits the price axis at P=$50 (where Q=0) and the quantity axis at Q=100 (where P=0). Qs=2P starts at the origin. Sketching those intercepts before solving catches sign errors. Qd=100-2P 与价格轴交于 P=$50(此时 Q=0),与 数量轴交于 Q=100(此时 P=0)。Qs=2P 从原点出 发。求解前先画出这些截距能抓住符号错误。 ! Demand vs quantity demanded; P-on-axis confusion 需求 vs 需求量;P 在轴上的混淆 Two recurring slips: (1) Although we write Q as a function of P, economists draw P on the vertical axis - do the algebra in whichever form is given, then map to the graph. (2) Set quantities equal, never prices - demand and supply share the same market price, so it is Qd = Qs that pins down P *. 两个常犯的失误:(1)虽然我们把 Q 写成 P 的函数,经济学家却把 P 画在纵轴 -- 用给定的形式做代数,再映射到图 上。(2)令数量相等,绝不令价格相等 -- 供求共用同一市场价格,所以是 Qd= Qs 锁定 P *。 AskSia Library · ECON10004 · 双语 Bilingual ★ Exam move - the equilibrium-first habit 考试技巧 -- 先求均衡的习惯 Whatever the policy to come - tax, subsidy, floor, quota, tariff - the first marks are always the free-market equilibrium: set Qd=Qs, get (P*, Q*), and label it on a clean diagram. Everything in Chapters 4-6 is measured as a change from this point. 无论接下来是什么政策 -- 税、补贴、价格下限、配额、关税 -- 头几分总是自由市场均衡:令 Qd=Qs,求出(P*, Q*),并在干净的图上标出它。第4-6章的一切都以与该点的变化来度量。 AskSia Library · ECON10004 · 双语 Bilingual CH 3 . PED EXAM CALC STAPLE - CHAPTER 3 Elasticity 弹性 How much quantity responds - and the formula the exam expects 数量反应多大 -- 考试要的公式 A demand curve tells you quantity falls when price rises. Elasticity tells you by how much - it turns the slope into a unit-free number you can compute, compare and link to revenue. This is a calculation staple: the course uses the point formula, taken as an absolute value, every time. 需求曲线告诉你价格上升时数量下降。弹性(elasticity)告诉你下降多少 -- 它把斜率变成一个无量纲、可计算、可比较、 可与收益挂钩的数字。这是计算常客:本课程每次都用点弹性公式,并取绝对值。 ★ What the exam asks here 这里考试问什么 Compute the point elasticity & = (dQ/dP)(P/Q) at a stated price; classify it as elastic / inelastic / unit-elastic; apply the total-revenue rule to say which way to move price to raise revenue; and identify income and cross-price elasticities by sign. Numeric-entry questions want a clean number such as & = - 1 or -3. 在给定价格处计算点弹性 &=(dQ/dP)(P/Q);将其分类为富有弹性/缺乏弹性/单位弹性;运用总收益法则说出价格往哪 边调能提高收益;并按符号辨认收入弹性与交叉价格弹性。填空题要的是 c =- 1 或-3 这类干净数字。 3. 1 Price elasticity of demand 3. 1 需求价格弹性 (PED) The price elasticity of demand (PED) is the percentage change in quantity demanded divided by the percentage change in price - the responsiveness of quantity to price. 需求价格弹性(PED) (price elasticity of demand) 是需求量的百分比变化除以价格的百分比变化––衡量数量对价格的反 应程度。 PRICE ELASTICITY OF DEMAND

• 2.2 剩余（CS/PS/TS）= 三个三角形

  • 三条面积公式（线性图必用）：每块剩余都是直角三角形
    • 面积：$\text{Area}=\frac12\times \text{base}\times \text{height}$（底是数量，高是价格差）[11]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfAskSia Library · ECON10004 · 双语 Bilingual 每个卖者都有一个边际成本(MC) -- 即供给曲线的高 度。他们收到市场价格。其间的缺口就是他们的收益。对所 有售出单位求和,生产者剩余(PS)就是供给曲线之上、 价格之下的面积。 THE THREE AREAS CS = 1/2 × base > height = 1/2 x Q* * (choke price - P*) PS = 1/2 × Q* x (P* - supply intercept) TS = CS + PS i The 'choke price' “窒息价格”(choke price) The choke price is the price so high that quantity demanded falls to zero - the vertical intercept of the demand curve. It is the top corner of the CS triangle, so you always need it to compute consumer surplus. 窒息价格(choke price)是高到使需求量降为零的价 格 -- 即需求曲线的纵轴截距。它是CS三角形的顶 角,所以算消费者剩余时永远用得上它。 ✓ Reading areas off a linear graph 从线性图上读取面积 Every surplus is a right triangle: area = 1/2 x base x height. The base is the quantity (measured along the horizontal axis); the height is the vertical price gap. Find the two intercepts and the equilibrium point, and all three areas drop out. 每个剩余都是直角三角形:面积=1/2×底×高。底是数量(沿横轴量),高是纵向价格差。找出两个截距和均衡点,三 块面积自然全出来。 AskSia Library · ECON10004 · 双语 Bilingual CH 4 . WORKED CHAPTER 4 . WORKED EXAMPLE WORKED . REAL NUMBERS The surplus calculation, end to end 剩余计算,从头到尾 Qd = 120 - 20P, Qs = 20P Qd = 120 - 20P, Qs = 20P This is the exact structure the exam reuses everywhere: solve for equilibrium, find the two intercepts, then compute three triangle areas. The numbers below are from the subject's own extra-practice set (L8). 这正是考试到处复用的结构:求均衡,找出两个截距,再计算三个三角形面积。下面的数字取自本科目自带的额外练习集 (L8)。 1 Equilibrium. Set Qd = Qs: 120 - 20P = 20P -+ 120 = 4OP - P* = 3. Then Q* = 20 x 3 = 60. 均衡。令 Qd= Qs: 120 - 20P= 20P→ 120= 40P→ P* = 3。则 Q* = 20× 3=60。 2 Choke price (demand intercept). Set Qd = 0: 120 - 20P = 0 -+ P = 6. The demand curve hits the price axis at $6. 窒息价格(choke price,需求截距)。令 Qd=0: 120- 20P=0→P=6。需求曲线在 $6 处碰到价格轴。 - 3 Supply intercept. Set Qs = 0: 20P = 0 -+ P = 0. Supply starts at the origin. 供给截距。 令 Qs = 0: 20P=0→ P=0。供给从原点起 步。 4 Consumer surplus. Triangle from P* = 3 up to the choke price 6, over Q* = 60: CS = 1/2 x 60 x (6 - 3) = 90. 消费者剩余(consumer surplus)。从 P *= 3 到窒息价格 6、横跨 Q *= 60 的三角形:CS=1/2 × 60×(6-3)= 90。 5 Producer surplus. Triangle from the supply intercept O up to P* = 3, over Q* = 60: PS = 1/2 x 60 × (3 - 0) = 90. 生产者剩余(producer surplus)。从供给截距 0 到 P* = 3、横跨 Q *= 60 的三角形:PS=1/2×60×(3-0)= 90. 6 Total surplus. TS = CS + PS = 90 + 90 = 180.
  • choke price（窒息价格）定义
    • “价格高到使需求量为 0 的价格”，即需求曲线的纵轴截距；算 $CS$ 必用。[11]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfAskSia Library · ECON10004 · 双语 Bilingual 每个卖者都有一个边际成本(MC) -- 即供给曲线的高 度。他们收到市场价格。其间的缺口就是他们的收益。对所 有售出单位求和,生产者剩余(PS)就是供给曲线之上、 价格之下的面积。 THE THREE AREAS CS = 1/2 × base > height = 1/2 x Q* * (choke price - P*) PS = 1/2 × Q* x (P* - supply intercept) TS = CS + PS i The 'choke price' “窒息价格”(choke price) The choke price is the price so high that quantity demanded falls to zero - the vertical intercept of the demand curve. It is the top corner of the CS triangle, so you always need it to compute consumer surplus. 窒息价格(choke price)是高到使需求量降为零的价 格 -- 即需求曲线的纵轴截距。它是CS三角形的顶 角,所以算消费者剩余时永远用得上它。 ✓ Reading areas off a linear graph 从线性图上读取面积 Every surplus is a right triangle: area = 1/2 x base x height. The base is the quantity (measured along the horizontal axis); the height is the vertical price gap. Find the two intercepts and the equilibrium point, and all three areas drop out. 每个剩余都是直角三角形:面积=1/2×底×高。底是数量(沿横轴量),高是纵向价格差。找出两个截距和均衡点,三 块面积自然全出来。 AskSia Library · ECON10004 · 双语 Bilingual CH 4 . WORKED CHAPTER 4 . WORKED EXAMPLE WORKED . REAL NUMBERS The surplus calculation, end to end 剩余计算,从头到尾 Qd = 120 - 20P, Qs = 20P Qd = 120 - 20P, Qs = 20P This is the exact structure the exam reuses everywhere: solve for equilibrium, find the two intercepts, then compute three triangle areas. The numbers below are from the subject's own extra-practice set (L8). 这正是考试到处复用的结构:求均衡,找出两个截距,再计算三个三角形面积。下面的数字取自本科目自带的额外练习集 (L8)。 1 Equilibrium. Set Qd = Qs: 120 - 20P = 20P -+ 120 = 4OP - P* = 3. Then Q* = 20 x 3 = 60. 均衡。令 Qd= Qs: 120 - 20P= 20P→ 120= 40P→ P* = 3。则 Q* = 20× 3=60。 2 Choke price (demand intercept). Set Qd = 0: 120 - 20P = 0 -+ P = 6. The demand curve hits the price axis at $6. 窒息价格(choke price,需求截距)。令 Qd=0: 120- 20P=0→P=6。需求曲线在 $6 处碰到价格轴。 - 3 Supply intercept. Set Qs = 0: 20P = 0 -+ P = 0. Supply starts at the origin. 供给截距。 令 Qs = 0: 20P=0→ P=0。供给从原点起 步。 4 Consumer surplus. Triangle from P* = 3 up to the choke price 6, over Q* = 60: CS = 1/2 x 60 x (6 - 3) = 90. 消费者剩余(consumer surplus)。从 P *= 3 到窒息价格 6、横跨 Q *= 60 的三角形:CS=1/2 × 60×(6-3)= 90。 5 Producer surplus. Triangle from the supply intercept O up to P* = 3, over Q* = 60: PS = 1/2 x 60 × (3 - 0) = 90. 生产者剩余(producer surplus)。从供给截距 0 到 P* = 3、横跨 Q *= 60 的三角形:PS=1/2×60×(3-0)= 90. 6 Total surplus. TS = CS + PS = 90 + 90 = 180.
  • 剩余计算套路（考试给分点）
    • (1) $Q_d=Q_s$ 得 $P^*,Q^*$
    • (2) 令 $Q_d=0$ 得 choke price；令 $Q_s=0$ 得供给截距
    • (3)
      • $CS=\frac12\cdot Q^*\cdot(\text{choke}-P^*)$
      • $PS=\frac12\cdot Q^*\cdot(P^*-\text{supply intercept})$
      • $TS=CS+PS$ 。[15]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfConsumer surplus is not total spending and producer surplus is not total revenue. CS is the gap between what buyers would pay and what they do pay; PS is the gap between the price received and marginal cost. Computing 'price x quantity' for a surplus is the most common error markers see. 消费者剩余不是总支出,生产者剩余不是总收入。CS 是买方愿意付与实际付之间的差;PS 是收到的价格与边际成本之 间的差。把剩余算成“价格×数量”是阅卷人见得最多的错误。 i Exam move - the surplus drill 考试技巧 -- 剩余计算套路 (1) Set Qd = Qs for P*, Q*. (2) Set each curve = 0 for the demand choke price and supply intercept. (3) CS = 1/2. Q *. (choke - P*); PS = 1/2. Q *. (P* - intercept); TS = CS + PS. (4) Any policy that moves Q below Q* carves a deadweight-loss triangle out of total surplus - that is the next chapter. (1) 令 Qd = Qs 求 P *、 Q *。 (2)令各曲线=0 求需求窒息价格与供给截距。(3) CS= 1/2·Q* · (窒息价-P*); PS = 1/2·Q *· (P* - 截距); TS= CS+ PS。(4)任何把 Q 压到Q*以下的政策都会从社会总剩余中切出一个无谓损失三角形 -- 那是下一章的内容。 AskSia Library · ECON10004 · 双语 Bilingual CH 5 . CONTROLS - CHAPTER 5 . GOVERNMENT IN THE MARKET MOST - TESTED CALC Controls, taxes & deadweight loss 管制、税收与无谓损失 Price ceilings, price floors, per-unit taxes, incidence, subsidies 价格上限、价格下限、单位税、税负归宿、补贴 When government steps into a market - capping rents, setting a minimum wage, taxing sugar, subsidising solar - it pushes the outcome away from the competitive equilibrium. Because that equilibrium maximised total surplus (Chapter 4), almost any intervention destroys some surplus: the deadweight loss. This chapter teaches the one calculation chain the exam returns to again and again. 当政府介入某市场 -- 设租金上限、定最低工资、对糖征税、补贴太阳能 -- 它会把结果推离竞争均衡。由于该均衡使社会总 剩余最大化(第4章),几乎任何干预都会毁掉一些剩余:即无谓损失(DWL)。本章教的就是考试一遍又一遍回归的那条计算 链。 ★ This is THE exam chapter 这是考试核心章节 Across the mined review sessions, the single most repeated worked problem is the chain equilibrium - elasticity - surplus - impose a policy - deadweight loss. It appears almost verbatim three times, marked 3+3+3+3+3. Price-control and policy MCQs add six more questions. If you drill one thing for this exam, drill the method on the next four pages. 在所有挖掘到的复习课里,被反复演练最多的一道题就是这条链:均衡→弹性→剩余→施加政策→无谓损失。它几 乎逐字出现三次,按3+3+3+3+3 计分。价格管制与政策类选择题又添六道。如果你只为这场考试钻一样东西,就钻接 下来四页的这套方法。 Two kinds of intervention 两类干预 1 . Price controls fix the price by law. A ceiling sets a legal maximum; a floor sets a legal minimum. They only bind - actually change behaviour - when set on the 'wrong' side of equilibrium. 1 · 价格管制用法律固定价格。价格上限(ceiling)设法定 最高价;价格下限(floor) 设法定最低价。只有设在均衡的 “错误”一侧时它们才有约束力 -- 即真正改变行为。 2 . Taxes & subsidies leave the price free but drive a wedge between what buyers pay and what sellers receive. A tax opens the wedge; a subsidy is its mirror image. 2 · 税与补贴让价格保持自由,却在买者所付与卖者所得之 间打入一个楔子(wedge)。税撑开楔子;补贴是它的镜 像。 Price ($) S ceiling Po shortage
  • 最常见大错（老师最爱扣）
    • CS 不是总支出、PS 不是总收入；把剩余算成 $P\times Q$ 是最常见错误。[15]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfConsumer surplus is not total spending and producer surplus is not total revenue. CS is the gap between what buyers would pay and what they do pay; PS is the gap between the price received and marginal cost. Computing 'price x quantity' for a surplus is the most common error markers see. 消费者剩余不是总支出,生产者剩余不是总收入。CS 是买方愿意付与实际付之间的差;PS 是收到的价格与边际成本之 间的差。把剩余算成“价格×数量”是阅卷人见得最多的错误。 i Exam move - the surplus drill 考试技巧 -- 剩余计算套路 (1) Set Qd = Qs for P*, Q*. (2) Set each curve = 0 for the demand choke price and supply intercept. (3) CS = 1/2. Q *. (choke - P*); PS = 1/2. Q *. (P* - intercept); TS = CS + PS. (4) Any policy that moves Q below Q* carves a deadweight-loss triangle out of total surplus - that is the next chapter. (1) 令 Qd = Qs 求 P *、 Q *。 (2)令各曲线=0 求需求窒息价格与供给截距。(3) CS= 1/2·Q* · (窒息价-P*); PS = 1/2·Q *· (P* - 截距); TS= CS+ PS。(4)任何把 Q 压到Q*以下的政策都会从社会总剩余中切出一个无谓损失三角形 -- 那是下一章的内容。 AskSia Library · ECON10004 · 双语 Bilingual CH 5 . CONTROLS - CHAPTER 5 . GOVERNMENT IN THE MARKET MOST - TESTED CALC Controls, taxes & deadweight loss 管制、税收与无谓损失 Price ceilings, price floors, per-unit taxes, incidence, subsidies 价格上限、价格下限、单位税、税负归宿、补贴 When government steps into a market - capping rents, setting a minimum wage, taxing sugar, subsidising solar - it pushes the outcome away from the competitive equilibrium. Because that equilibrium maximised total surplus (Chapter 4), almost any intervention destroys some surplus: the deadweight loss. This chapter teaches the one calculation chain the exam returns to again and again. 当政府介入某市场 -- 设租金上限、定最低工资、对糖征税、补贴太阳能 -- 它会把结果推离竞争均衡。由于该均衡使社会总 剩余最大化(第4章),几乎任何干预都会毁掉一些剩余:即无谓损失(DWL)。本章教的就是考试一遍又一遍回归的那条计算 链。 ★ This is THE exam chapter 这是考试核心章节 Across the mined review sessions, the single most repeated worked problem is the chain equilibrium - elasticity - surplus - impose a policy - deadweight loss. It appears almost verbatim three times, marked 3+3+3+3+3. Price-control and policy MCQs add six more questions. If you drill one thing for this exam, drill the method on the next four pages. 在所有挖掘到的复习课里,被反复演练最多的一道题就是这条链:均衡→弹性→剩余→施加政策→无谓损失。它几 乎逐字出现三次,按3+3+3+3+3 计分。价格管制与政策类选择题又添六道。如果你只为这场考试钻一样东西,就钻接 下来四页的这套方法。 Two kinds of intervention 两类干预 1 . Price controls fix the price by law. A ceiling sets a legal maximum; a floor sets a legal minimum. They only bind - actually change behaviour - when set on the 'wrong' side of equilibrium. 1 · 价格管制用法律固定价格。价格上限(ceiling)设法定 最高价;价格下限(floor) 设法定最低价。只有设在均衡的 “错误”一侧时它们才有约束力 -- 即真正改变行为。 2 . Taxes & subsidies leave the price free but drive a wedge between what buyers pay and what sellers receive. A tax opens the wedge; a subsidy is its mirror image. 2 · 税与补贴让价格保持自由,却在买者所付与卖者所得之 间打入一个楔子(wedge)。税撑开楔子;补贴是它的镜 像。 Price ($) S ceiling Po shortage

• 2.3 点弹性（本课指定方法）

  • 点弹性公式（PED）：
    • $$E=\left(\frac{dQ}{dP}\right)\left(\frac{P}{Q}\right)$$
    • 需求向下所以 $dQ/dP<0$，本课通常用 绝对值 $|E|$ 来分类。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.[20]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfE = %△Q %AP - point form & = (dQ/dP) x (P/Q) Because demand slopes down, dQ/dP is negative and & comes out negative - so the course reports the absolute value |s| and classifies on that. 由于需求向下倾斜,dQ/dP 为负,& 算出来是负的 -- 所以本课程报告绝对值 |e| 并据此分类。 § The point formula IS the course's method 点公式就是本课的方法 ECON10004 computes PED by the point method: take dQ/dP (for a linear demand Q = a - bP this is just -b, the coefficient on P), then multiply by the P/Q at the point of interest, and take the absolute value. No midpoint formula is needed - the slope is constant, but P/Q changes as you slide along the curve, so & differs at every point. ECON10004 用点法算 PED:取 dQ/dP (对线性需求 Q= a - bP就是-b,即P的系数),再乘以目标点的 P/Q,取 绝对值。无需中点公式 -- 斜率虽恒定,但P/Q 随你沿曲线滑动而变,所以 每点都不同。 AskSia Library · ECON10004 · 双语 Bilingual The three regions 三个区域 Name Meaning > 1 Elastic Q responds more than proportionally to price = 1 Unit-elastic Q changes in the same proportion as price < 1 Inelastic Q barely responds to price AskSia Library · ECON10004 · 双语 Bilingual CH 3 . TR RULE - CHAPTER 3 (CONT. ) Shapes, determinants & the total-revenue rule 形状、决定因素与总收益法则 What elastic looks like, why, and what it does to revenue 弹性大什么样、为何、对收益有何影响 Price ($) D Quantity Elastic (|E|>1): a flat demand curve - a small price change brings a large quantity change. Many substitutes, plenty of time to adjust. 富有弹性(le|>1):一条平坦的需求曲线 -- 小幅价 格变化带来大幅数量变化。替代品多,调整时间充 裕。
  • 线性需求 $Q=a-bP$ 的快速法
    • $\frac{dQ}{dP}=-b$（就是 $P$ 的系数取负），再乘 $P/Q$。[20]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfE = %△Q %AP - point form & = (dQ/dP) x (P/Q) Because demand slopes down, dQ/dP is negative and & comes out negative - so the course reports the absolute value |s| and classifies on that. 由于需求向下倾斜,dQ/dP 为负,& 算出来是负的 -- 所以本课程报告绝对值 |e| 并据此分类。 § The point formula IS the course's method 点公式就是本课的方法 ECON10004 computes PED by the point method: take dQ/dP (for a linear demand Q = a - bP this is just -b, the coefficient on P), then multiply by the P/Q at the point of interest, and take the absolute value. No midpoint formula is needed - the slope is constant, but P/Q changes as you slide along the curve, so & differs at every point. ECON10004 用点法算 PED:取 dQ/dP (对线性需求 Q= a - bP就是-b,即P的系数),再乘以目标点的 P/Q,取 绝对值。无需中点公式 -- 斜率虽恒定,但P/Q 随你沿曲线滑动而变,所以 每点都不同。 AskSia Library · ECON10004 · 双语 Bilingual The three regions 三个区域 Name Meaning > 1 Elastic Q responds more than proportionally to price = 1 Unit-elastic Q changes in the same proportion as price < 1 Inelastic Q barely responds to price AskSia Library · ECON10004 · 双语 Bilingual CH 3 . TR RULE - CHAPTER 3 (CONT. ) Shapes, determinants & the total-revenue rule 形状、决定因素与总收益法则 What elastic looks like, why, and what it does to revenue 弹性大什么样、为何、对收益有何影响 Price ($) D Quantity Elastic (|E|>1): a flat demand curve - a small price change brings a large quantity change. Many substitutes, plenty of time to adjust. 富有弹性(le|>1):一条平坦的需求曲线 -- 小幅价 格变化带来大幅数量变化。替代品多,调整时间充 裕。
  • 收益（Total Revenue）规则
    • 若需求缺乏弹性 $|E|<1$：提价会提高总收益；
    • 若富有弹性 $|E|>1$：降价会提高总收益；
    • 总收益在 $|E|=1$ 达峰。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 税负归宿（incidence）规则（选择题超爱考）
    • 弹性较小的一方承担更多税负（更“走不开”）。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.[16]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfI tax revenue I deadweight loss AskSia Library · ECON10004 · 双语 Bilingual - Deadweight loss = the part of lost CS + PS that nobody captures (the red triangle). 无谓损失 = 损失的 CS+PS 中无人捕获的那部分(红色三 角)。 Tax incidence - who actually bears it 税负归宿 -- 谁真正承担 The statutory payer (whoever writes the cheque) is irrelevant. The economic burden is split by relative elasticity: the side that can least escape - the less elastic (steeper) side - absorbs the larger share of the tax. 法定(statutory)缴款方(写支票的那一方)无关紧要。经济负担按相对弹性分摊:最无法逃脱的一方 -- 弹性较小(较陡)的一方 -- 承担更大份额的税。 INCIDENCE RULE The less-elastic side bears MORE of the tax. Buyer's share * Seller's share = Es + | Eal Intuition: an inelastic side keeps trading even as the price moves against it, so the price moves a long way against it - it can't walk away. An elastic side flees a small price move, so the price barely shifts toward it. Demand for cigarettes is inelastic - smokers (buyers) bear most of a tobacco tax; if supply were the inelastic side, sellers would. 直觉:弹性小的一方即便价格对其不利仍继续交易,所以价格会大幅向其不利方向移动 -- 它走不掉。弹性大的一方一遇小幅 价格变动就逃离,所以价格几乎不向它移动。香烟需求缺乏弹性→烟民(买者)承担烟草税的大部分;若供给是缺乏弹性的 一方,就由卖者承担。 ! Don't confuse statutory with economic incidence 别混淆法定归宿与经济归宿 "The tax is on sellers" tells you nothing about who really pays. A sugar-tax MCQ in the review set hinges on exactly this: the answer is decided by which side is less elastic, not by who hands the money to the tax office. “税征在卖方身上”对真正谁付税毫无说明。复习题库里一道糖税选择题正是卡在这点上:答案由哪一方弹性更小决定, 而非由谁把钱交给税务局决定。 - AskSia Library · ECON10004 · 双语 Bilingual CH 5 . SIGNATURE CHAIN - CHAPTER 5 . THE SIGNATURE WORKED CHAIN MEMORISE THIS Equilibrium - elasticity - surplus - tax - DWL 均衡→弹性→剩余→税收→DWL QD = 100 - SP, Qs = SP, then a $2 per-unit tax QD = 100 -5P,Qs=5P,再加 $2 单位税 This is the exam's most-repeated problem, transcribed from the review sessions (RS4/RS4a Q7) and marked 3+3+3+3+3. Learn the five moves and the numbers fall out cleanly every time. 这是考试最常重复的题目,转录自复习课(RS4/RS4a Q7),按3+3+3+3+3评分。学会这五个动作,数字每次都干净利落 地算出来。 1 Equilibrium. 100 - 5P = 5P -+ 100 = 10P - P* = 10, Q* = 5 x10 = 50. 均衡。100-5P=5P→100=10P→P *= 10, Q *= 5 × 10 = 50. 2 Point elasticities at equilibrium. Ed = (dQ/dP) (P/Q) = (-5)(10/50) = (-1); Es =(5)(10/50) = (+1). Equal magnitudes - the tax splits 50/50. 均衡处的点弹性。Ed =(dQ/dP)(P/Q) = (-5)(10/50) = (-1); Es =(5)(10/50)=(+1)。绝对值相等→ 税负五五分 摊。 3 Surplus before tax. Demand choke price (Qd = 0): P = 20. CS = 1/2 × 50 x (20 -10) = 250; PS = 1/2 ×50 x (10 - 0) = 250. 税前剩余。需求窒息价格(Qd=0): P=20。CS= 1/2× 50 × (20 -10) = 250; PS = 1/2 × 50×(10-0)=250.
    • 法定纳税方（谁写支票）不重要，重要的是相对弹性。[16]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfI tax revenue I deadweight loss AskSia Library · ECON10004 · 双语 Bilingual - Deadweight loss = the part of lost CS + PS that nobody captures (the red triangle). 无谓损失 = 损失的 CS+PS 中无人捕获的那部分(红色三 角)。 Tax incidence - who actually bears it 税负归宿 -- 谁真正承担 The statutory payer (whoever writes the cheque) is irrelevant. The economic burden is split by relative elasticity: the side that can least escape - the less elastic (steeper) side - absorbs the larger share of the tax. 法定(statutory)缴款方(写支票的那一方)无关紧要。经济负担按相对弹性分摊:最无法逃脱的一方 -- 弹性较小(较陡)的一方 -- 承担更大份额的税。 INCIDENCE RULE The less-elastic side bears MORE of the tax. Buyer's share * Seller's share = Es + | Eal Intuition: an inelastic side keeps trading even as the price moves against it, so the price moves a long way against it - it can't walk away. An elastic side flees a small price move, so the price barely shifts toward it. Demand for cigarettes is inelastic - smokers (buyers) bear most of a tobacco tax; if supply were the inelastic side, sellers would. 直觉:弹性小的一方即便价格对其不利仍继续交易,所以价格会大幅向其不利方向移动 -- 它走不掉。弹性大的一方一遇小幅 价格变动就逃离,所以价格几乎不向它移动。香烟需求缺乏弹性→烟民(买者)承担烟草税的大部分;若供给是缺乏弹性的 一方,就由卖者承担。 ! Don't confuse statutory with economic incidence 别混淆法定归宿与经济归宿 "The tax is on sellers" tells you nothing about who really pays. A sugar-tax MCQ in the review set hinges on exactly this: the answer is decided by which side is less elastic, not by who hands the money to the tax office. “税征在卖方身上”对真正谁付税毫无说明。复习题库里一道糖税选择题正是卡在这点上:答案由哪一方弹性更小决定, 而非由谁把钱交给税务局决定。 - AskSia Library · ECON10004 · 双语 Bilingual CH 5 . SIGNATURE CHAIN - CHAPTER 5 . THE SIGNATURE WORKED CHAIN MEMORISE THIS Equilibrium - elasticity - surplus - tax - DWL 均衡→弹性→剩余→税收→DWL QD = 100 - SP, Qs = SP, then a $2 per-unit tax QD = 100 -5P,Qs=5P,再加 $2 单位税 This is the exam's most-repeated problem, transcribed from the review sessions (RS4/RS4a Q7) and marked 3+3+3+3+3. Learn the five moves and the numbers fall out cleanly every time. 这是考试最常重复的题目,转录自复习课(RS4/RS4a Q7),按3+3+3+3+3评分。学会这五个动作,数字每次都干净利落 地算出来。 1 Equilibrium. 100 - 5P = 5P -+ 100 = 10P - P* = 10, Q* = 5 x10 = 50. 均衡。100-5P=5P→100=10P→P *= 10, Q *= 5 × 10 = 50. 2 Point elasticities at equilibrium. Ed = (dQ/dP) (P/Q) = (-5)(10/50) = (-1); Es =(5)(10/50) = (+1). Equal magnitudes - the tax splits 50/50. 均衡处的点弹性。Ed =(dQ/dP)(P/Q) = (-5)(10/50) = (-1); Es =(5)(10/50)=(+1)。绝对值相等→ 税负五五分 摊。 3 Surplus before tax. Demand choke price (Qd = 0): P = 20. CS = 1/2 × 50 x (20 -10) = 250; PS = 1/2 ×50 x (10 - 0) = 250. 税前剩余。需求窒息价格(Qd=0): P=20。CS= 1/2× 50 × (20 -10) = 250; PS = 1/2 × 50×(10-0)=250.

• 2.4 税与无谓损失（DWL）

  • 税楔 wedge：买者付 $P_b$，卖者收 $P_s$，单位税 $t$：
    • $$P_b-P_s=t$$ [8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 无谓损失（DWL）公式（最常用版本）
    • $$DWL=\frac12\times t\times \Delta Q$$ [8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.

• 2.5 垄断（Monopoly）

  • 产量规则（必须背）：
    • 先令 $MR=MC$ 求 $Q$，再从需求曲线读 $P$（不要从 MR 读价格）。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 线性需求的 MR 公式（本课直接给你了）
    • 若 $P=a-bQ$，则
      • $$MR=a-2bQ$$ [8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 重要结论：垄断下通常 $P>MC$，会产生无谓损失。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.

• 2.6 成本与竞争（Perfect competition + 成本）

  • 竞争厂商产量规则：$P=MC$。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 短期停业（shutdown）规则：若 $P<AVC$ 则停业（连可变成本都覆盖不了）。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 长期结果：自由进入使 $P\to \min ATC$，经济利润 $\to 0$。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.

• 2.7 市场失灵（外部性 / 公共物品 / 信息不对称）

  • 负外部性关键不等式：$SMC>PMC$，市场会“过度生产”。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 庇古税（Pigouvian tax）：最优矫正税 = 边际外部成本（不是总外部成本）。[7]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf- 选(a)的原因:弹性较小的一方承担更多 -- 它无法走开。(b)法定纳税方与经济税负归宿无关。(c)五五分摊需要弹性相等。 (d) 政府收的是税款,不承担税负。 - Q5 MCQ competition vs monopoly rule Which output rule is correct? 哪条产量法则是正确的? (a) Competitive firm: P = MC; monopolist: MR = MC - correct (b) Both produce where P = MC (c) Competitive firm: MR = MC; monopolist: P = MC (d) Both produce where MR = MC and P = MR Why (a) : a price-taker has P = MR, so P = MC; a monopolist faces MR < P, sets MR = MC then prices off demand. (b)/(c) swap the rules. (d) P = MR only holds under competition. 选(a)的原因:价格接受者 P=MR,故 P= MC;垄断者面对 MR <P,先令 MR= MC 再到需求曲线定价。(b)/(c)把法则 弄反了。(d)P = MR仅在竞争下成立。 Pigouvian tax & public goods 06 MCQ Which statement is correct? 哪条陈述是正确的? (a) A Pigouvian tax equals the marginal external cost; a public good is non-rival and non- excludable - correct (b) A Pigouvian tax equals the total external cost (c) A public good is rival but non-excludable (d) A public good is excludable but non-rival AskSia Library · ECON10004 · 双语 Bilingual - Why (a): the optimal corrective tax = the marginal external cost, and a pure public good is both non- rival (my use does not reduce yours) and non-excludable (cannot keep non-payers out). (b) uses total, not marginal. (c) describes a common resource. (d) describes a club good. 选(a)的原因:最优矫正税 = 边际外部成本,而纯公共物品既非竞争性(我用了不减少你用)又非排他性(无法把不付费者 挡在外)。(b)用了总额而非边际。(c)描述的是公共资源。(d)描述的是俱乐部物品。 ✓ MCQ technique - eliminate, don't just recognise 选择题技巧 -- 排除法,别只靠认得 Each wrong option here is a real concept in the wrong slot: a shift instead of a movement, producer surplus labelled as consumer surplus, total external cost instead of marginal, a common resource called a public good. If you can name what each distractor actually describes, the answer is unambiguous - and you have revised four concepts per question. 这里每个错误选项都是放错位置的真实概念:把移动说成沿线变动、把生产者剩余标成消费者剩余、把总外部成本当成 边际、把公共资源叫成公共物品。如果你能说出每个干扰项实际描述的是什么,答案就毫不含糊 -- 而且你每道题复习 了四个概念。 AskSia Library · ECON10004 · 双语 Bilingual CH 14 . EXAM MORNING - CHAPTER 14 . EXAM MORNING CLEARING THE HURDLE If you remember nothing else 其余都忘也记住这些[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 公共物品定义（选择题爱考定义）
    • 公共物品是：非竞争性（non-rival） + 非排他性（non-excludable）。[7]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf- 选(a)的原因:弹性较小的一方承担更多 -- 它无法走开。(b)法定纳税方与经济税负归宿无关。(c)五五分摊需要弹性相等。 (d) 政府收的是税款,不承担税负。 - Q5 MCQ competition vs monopoly rule Which output rule is correct? 哪条产量法则是正确的? (a) Competitive firm: P = MC; monopolist: MR = MC - correct (b) Both produce where P = MC (c) Competitive firm: MR = MC; monopolist: P = MC (d) Both produce where MR = MC and P = MR Why (a) : a price-taker has P = MR, so P = MC; a monopolist faces MR < P, sets MR = MC then prices off demand. (b)/(c) swap the rules. (d) P = MR only holds under competition. 选(a)的原因:价格接受者 P=MR,故 P= MC;垄断者面对 MR <P,先令 MR= MC 再到需求曲线定价。(b)/(c)把法则 弄反了。(d)P = MR仅在竞争下成立。 Pigouvian tax & public goods 06 MCQ Which statement is correct? 哪条陈述是正确的? (a) A Pigouvian tax equals the marginal external cost; a public good is non-rival and non- excludable - correct (b) A Pigouvian tax equals the total external cost (c) A public good is rival but non-excludable (d) A public good is excludable but non-rival AskSia Library · ECON10004 · 双语 Bilingual - Why (a): the optimal corrective tax = the marginal external cost, and a pure public good is both non- rival (my use does not reduce yours) and non-excludable (cannot keep non-payers out). (b) uses total, not marginal. (c) describes a common resource. (d) describes a club good. 选(a)的原因:最优矫正税 = 边际外部成本,而纯公共物品既非竞争性(我用了不减少你用)又非排他性(无法把不付费者 挡在外)。(b)用了总额而非边际。(c)描述的是公共资源。(d)描述的是俱乐部物品。 ✓ MCQ technique - eliminate, don't just recognise 选择题技巧 -- 排除法,别只靠认得 Each wrong option here is a real concept in the wrong slot: a shift instead of a movement, producer surplus labelled as consumer surplus, total external cost instead of marginal, a common resource called a public good. If you can name what each distractor actually describes, the answer is unambiguous - and you have revised four concepts per question. 这里每个错误选项都是放错位置的真实概念:把移动说成沿线变动、把生产者剩余标成消费者剩余、把总外部成本当成 边际、把公共资源叫成公共物品。如果你能说出每个干扰项实际描述的是什么,答案就毫不含糊 -- 而且你每道题复习 了四个概念。 AskSia Library · ECON10004 · 双语 Bilingual CH 14 . EXAM MORNING - CHAPTER 14 . EXAM MORNING CLEARING THE HURDLE If you remember nothing else 其余都忘也记住这些[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
  • 市场失灵大题“给分套路”（按步骤写就有分）
    • (1) 先辨认失灵类型（外部性/公共物品/公共资源/信息不对称）
    • (2) 用私人曲线求 $Q_{market}$（如 $PMB=PMC$）
    • (3) 用社会曲线求有效率 $Q^*$（如 $MB=SMC$）
    • (4) $DWL$ 是 $Q_m$ 与 $Q^*$ 之间的三角形，高是外部成本/收益
    • (5) 政策：负外部性用庇古税=边际外部成本；正外部性用补贴=边际外部收益；当事方少且产权清晰可谈判；公共物品可政府供给。[13]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdftype / before quality contract used-car "lemons" Moral action / after hazard effort contract risky behaviour once insured Remedies for both internalise the missing information: warranties and certification signal quality; lemon laws and reputation systems penalise hiding it; deductibles and monitoring curb moral hazard. 两类问题的解法都在于把缺失的信息内部化:保修与认证可 传递质量信号;柠檬法和声誉系统惩罚隐瞒;免赔额与监督 则遏制道德风险。 AskSia Library · ECON10004 · 双语 Bilingual ★ Recap - the market-failure exam move 回顾 -市场失灵的考试技巧 (1) Identify the failure - externality (which side, which sign?), public good, common resource, or asymmetric information. (2) Find Q_market from the private curves (PMB = PMC). (3) Find Q* from the social curves (MB = SMC, or SMB = PMC). (4) The DWL is the triangle between Qm and Q*, with height the external cost/benefit. (5) The fix: Pigouvian tax = marginal external cost (negative), subsidy = marginal external benefit (positive); or Coasian bargaining when parties are few and rights are clear; or government provision for public goods. (1) 辨认失灵类型 -- 外部性(哪一侧、什么符号?)、公共物品、公共资源还是信息不对称(asymmetric information)。(2)由私人曲线求 Q_市场(PMB=PMC)。(3)由社会曲线求 Q* (MB = SMC,或 SMB=PMC)。(4) DWL 是 Qm 与 Q* 之间的三角形,高为外部成本/收益。(5)解法:庇古税=边际外部成本(负外部性),补贴= 边际 外部收益(正外部性);或当事方少、产权清晰时用科斯式谈判;或公共物品由政府提供。 AskSia Library · ECON10004 · 双语 Bilingual CH 12 . GAME THEORY - CHAPTER 12 . GAME THEORY STRATEGY When your best move depends on theirs 最优应对取决于对方时 Payoff matrix . dominant strategy . Nash equilibrium . the prisoner's dilemma 支付矩阵 · 占优策略 · 纳什均衡· 囚徒困境 In perfect competition and monopoly a firm could ignore individual rivals. In an oligopoly - a few large firms - that breaks down: each firm's best move depends on what the others do. Game theory is the toolkit for these strategic situations, and its central result is unsettling: rational players, each acting in self-interest, can land everyone in an outcome they all dislike. 在完全竞争(perfect competition) 和垄断(monopoly)中,企业可以不理会单个对手。但在寡头垄断(oligopoly,少数几 家大企业)里,这一点崩溃了:每家企业的最佳行动都取决于其他企业怎么做。博弈论(game theory)正是分析这类策略性 情形的工具,而它的核心结论令人不安:理性的参与者各自追求自身利益,却可能把所有人推入一个谁都不喜欢的结局。 ★ What the exam does with this 考试如何考这一点 You will be handed a 2×2 payoff matrix and asked to find the equilibrium. The reliable method: (1) for each player, check whether one strategy beats the other no matter what the rival does - that is a dominant strategy. (2) The cell where each player is best-responding to the other is the Nash equilibrium - no one can gain by deviating alone. Be ready to identify it as a prisoner's dilemma and explain why the firms can't sustain the cooperative outcome.

• 2.8 贸易与关税（Tariff）

  • 关税题最常丢分点：DWL 不是一个三角形，而是两个（同时扭曲生产与消费）。[17]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfNet effect of the tariff — two DWL triangles Why economists prefer a subsidy to a tariff 经济学家为何偏好补贴胜过关税 To raise domestic production by a given amount, a production subsidy distorts only the production side - one DWL triangle. A tariff doing the same job also raises the consumer price, adding the consumption-distortion triangle - two triangles. Same producer gain, but the tariff destroys more total surplus. 要把国内产量提高给定的量,生产补贴只扭曲生产侧 -- 一个DWL三角形。而做同样工作的关税还会抬高消费者价格,添上 消费扭曲三角形 -- 两个三角形。生产者收益相同,但关税毁掉更多社会总剩余。 i Worked - carrot import tariff (RS2-4pm Q2) 例题 -- 胡萝卜进口关税(RS2-4pm Q2) Open economy Qd = 500 - 3P, Qs = P - 100, world price $120. At $120: Qd = 140, Qs = 20-+ imports = 120. Add a $10 tariff - price $130: Qd = 110, Qs = 30 -+ imports = 80. Imports fall by 40 tons - and two small DWL triangles open between the old and new quantities. 开放经济 Qd = 500 - 3P,Qs = P-100,世界价格 $120。在 $120: Qd = 140,Qs = 20→ 进口=120。加征 $10 关税→价格 $130: Qd = 110,Qs = 30→ 进口= 80。进口减少 40 吨 -- 并在新旧数量之间张开两个小的 DWL 三 角形。 ! Count BOTH triangles 两个三角形都要算 On import tariffs the most-missed mark is the second triangle. A tariff # a domestic tax: it distorts both production (too much made at home) and consumption (too little bought). If your tariff diagram shows only one DWL triangle, you have under-counted the welfare loss. 进口关税题里最常丢的分是第二个三角形。关税≠国内税:它同时扭曲生产(国内产太多)和消费(买得太少)。如果 你的关税图只画了一个DWL 三角形,你就少算了福利损失。 AskSia Library · ECON10004 · 双语 Bilingual i Exam move - the trade drill 考试技巧 -- 贸易计算套路 (1) Find the autarky P* from Qd = Qs. (2) Compare Pw: below - import, above - export. (3) At Pw, read Qd and Qs; the gap is imports/exports. (4) CS & PS as triangles against the world-price line. (5) A tariff raises the line by t - recompute imports, add tariff revenue, and shade the two DWL triangles. - (1)由 Qd = Qs 求自给自足 P *。 (2)比较 Pw:低于则进口,高于则出口。(3)在 Pw 处读出 Qd 与 Qs,差额即进口/出 口量。(4)对着世界价格线把 CS与 PS 作为三角形。(5)关税把价格线抬高 t -- 重算进口、加上关税收入,并把两个 DWL 三角形涂阴影。 AskSia Library · ECON10004 · 双语 Bilingual CH 7 . COSTS - CHAPTER 7 . PRODUCTION & COSTS BEHIND SUPPLY What it costs the firm to make the goods 厂商造货的成本 Economic cost . sunk vs fixed vs variable . the production function 经济成本 · 沉没/固定/可变·生产函数 Supply curves do not fall from the sky - they come from a firm's costs. Before we can ask how much should a firm produce, we need to measure cost the way an economist does, sort costs by whether they actually matter for a decision, and see where the familiar U-shaped curves come from. That is this chapter; the next one puts these curves to work. 供给曲线不是凭空掉下来的 -- 它来自厂商的成本。在能问厂商应生产多少之前,我们得用经济学家的方式衡量成本、按是否 真正影响决策对成本归类,并看出那些熟悉的U形曲线从何而来。这就是本章;下一章则让这些曲线发挥作用。 ★ What the exam does with this 考试如何考这一点
  • 贸易计算套路
    • (1) 自给自足：$Q_d=Q_s$ 求 $P^*$
    • (2) 比较世界价 $P_w$：$P_w$ 更低→进口；更高→出口
    • (3) 在 $P_w$ 读 $Q_d,Q_s$，差额是进出口
    • (4) 把 $CS,PS$ 当三角形对着世界价格线算
    • (5) 关税把价格线抬高 $t$：重算进口 + 加关税收入 + 画两个 $DWL$ 三角形。[17]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfNet effect of the tariff — two DWL triangles Why economists prefer a subsidy to a tariff 经济学家为何偏好补贴胜过关税 To raise domestic production by a given amount, a production subsidy distorts only the production side - one DWL triangle. A tariff doing the same job also raises the consumer price, adding the consumption-distortion triangle - two triangles. Same producer gain, but the tariff destroys more total surplus. 要把国内产量提高给定的量,生产补贴只扭曲生产侧 -- 一个DWL三角形。而做同样工作的关税还会抬高消费者价格,添上 消费扭曲三角形 -- 两个三角形。生产者收益相同,但关税毁掉更多社会总剩余。 i Worked - carrot import tariff (RS2-4pm Q2) 例题 -- 胡萝卜进口关税(RS2-4pm Q2) Open economy Qd = 500 - 3P, Qs = P - 100, world price $120. At $120: Qd = 140, Qs = 20-+ imports = 120. Add a $10 tariff - price $130: Qd = 110, Qs = 30 -+ imports = 80. Imports fall by 40 tons - and two small DWL triangles open between the old and new quantities. 开放经济 Qd = 500 - 3P,Qs = P-100,世界价格 $120。在 $120: Qd = 140,Qs = 20→ 进口=120。加征 $10 关税→价格 $130: Qd = 110,Qs = 30→ 进口= 80。进口减少 40 吨 -- 并在新旧数量之间张开两个小的 DWL 三 角形。 ! Count BOTH triangles 两个三角形都要算 On import tariffs the most-missed mark is the second triangle. A tariff # a domestic tax: it distorts both production (too much made at home) and consumption (too little bought). If your tariff diagram shows only one DWL triangle, you have under-counted the welfare loss. 进口关税题里最常丢的分是第二个三角形。关税≠国内税:它同时扭曲生产(国内产太多)和消费(买得太少)。如果 你的关税图只画了一个DWL 三角形,你就少算了福利损失。 AskSia Library · ECON10004 · 双语 Bilingual i Exam move - the trade drill 考试技巧 -- 贸易计算套路 (1) Find the autarky P* from Qd = Qs. (2) Compare Pw: below - import, above - export. (3) At Pw, read Qd and Qs; the gap is imports/exports. (4) CS & PS as triangles against the world-price line. (5) A tariff raises the line by t - recompute imports, add tariff revenue, and shade the two DWL triangles. - (1)由 Qd = Qs 求自给自足 P *。 (2)比较 Pw:低于则进口,高于则出口。(3)在 Pw 处读出 Qd 与 Qs,差额即进口/出 口量。(4)对着世界价格线把 CS与 PS 作为三角形。(5)关税把价格线抬高 t -- 重算进口、加上关税收入,并把两个 DWL 三角形涂阴影。 AskSia Library · ECON10004 · 双语 Bilingual CH 7 . COSTS - CHAPTER 7 . PRODUCTION & COSTS BEHIND SUPPLY What it costs the firm to make the goods 厂商造货的成本 Economic cost . sunk vs fixed vs variable . the production function 经济成本 · 沉没/固定/可变·生产函数 Supply curves do not fall from the sky - they come from a firm's costs. Before we can ask how much should a firm produce, we need to measure cost the way an economist does, sort costs by whether they actually matter for a decision, and see where the familiar U-shaped curves come from. That is this chapter; the next one puts these curves to work. 供给曲线不是凭空掉下来的 -- 它来自厂商的成本。在能问厂商应生产多少之前,我们得用经济学家的方式衡量成本、按是否 真正影响决策对成本归类,并看出那些熟悉的U形曲线从何而来。这就是本章;下一章则让这些曲线发挥作用。 ★ What the exam does with this 考试如何考这一点

3）必会定义/判断题清单（MCQ 半壁江山）

• dominant strategy（占优策略）：不管对手怎么选，你都最优的策略。[2]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf重复博弈与合作 If the game is played once, defection wins and cooperation is doomed. But oligopolists meet repeatedly. With an indefinite horizon, a firm can sustain the cooperative price by threatening to punish a cheater - for example, matching any price cut forever after. If the long-run loss from triggering that price war exceeds the one-off gain from cheating, cooperation can hold. This is how some collusion survives in practice, and why competition law watches repeated-interaction industries closely. 若博弈只玩一次,背叛取胜,合作注定失败。但寡头之间反 复相遇。在无限期视角下,企业可以靠威胁惩罚作弊者来维 持合作价 -- 例如从此永远跟降。若触发价格战的长期损失 超过作弊的一次性收益,合作就能维持。这就是现实中部分 合谋得以存续的原因,也是竞争法密切关注反复互动行业的 原因。 AskSia Library · ECON10004 · 双语 Bilingual i Recap - Chapter 12 in six lines 回顾 -- 第12章六行速记 (1) Game theory handles strategic settings (oligopoly) where your payoff depends on others' choices. (2) Read the payoff matrix: row payoff first, column second. (3) A dominant strategy is best regardless of the rival; play it. (4) A Nash equilibrium is where each best-responds - no one deviates alone (stable, not necessarily efficient). (5) The prisoner's dilemma: individually rational - collectively bad; both confess / both compete. (6) Cartels are unstable - each member gains by cheating; only repeated play with credible punishment can sustain cooperation. (1) 博弈论处理策略性情境(寡头),你的收益取决于他人的选择。(2)读收益矩阵:行收益在前,列收益在后。(3)占优 策略是无论对手怎样都最优的;打它。(4)纳什均衡是各自做最优反应 -- 没人单独偏离(稳定,未必有效)。(5)囚徒困 境:个体理性→集体糟糕;双双认罪/双双竞争。(6)卡特尔不稳定 -- 每个成员靠作弊获益;只有带可信惩罚的反复博 弈才能维持合作。 AskSia Library · ECON10004 · 双语 Bilingual CH 13 . PRACTICE P1 - CHAPTER 13 . PRACTICE BANK DRILL TO EXAM STANDARD Drill the exam, with full solutions 刷考题,附完整解答 Six graded problems in the real review-session style - worked end to end 六道分级题,真实复习课风格 -- 全程解答 These are exam-style problems, built on the real review-session and tutorial templates: multi-part calculation, a graph to draw, and a MCQ set. Every number is verified against this subject's own worked solutions. Treat each one as the real thing first; read the worked answer second. 这些是考试题型的习题,依据真实的复习课与习题课模板编排:多问计算、需作图的题、以及一组选择题。每个数字都已对照 本科目自己的标准解答核验。请先把每道题当作真考来做,之后再看解析。 - ★ How to use this bank 如何使用这个题库 Cover the solution. Work each problem on paper before you read a single line of the answer - recognition is not recall. Budget ~1 minute per mark. A 15-mark problem is a 15-minute problem; if you stall, move on and return. Always draw and fully label the graph - axes, both curves, equilibrium, and the shaded CS / PS / DWL. Graph marks are the easiest marks in the paper. Reconcile at the end: CS + PS + revenue + DWL must add back to the original total surplus, every time. 盖住答案。读到答案的任何一行之前,先在纸上把每 道题做出来 -- 认得出不等于答得出。每分预算约1 分钟。一道15分的题就是15 分钟的题;卡住了就跳 过、稍后回来。永远画出并完整标注图形 -- 坐标 轴、两条曲线、均衡点,以及涂好阴影的 CS/ PS / DWL。图形分是全卷最容易拿的分。最后做对账:CS + PS+ 收入 + DWL 每次都必须加回到原始的社会总 剩余。 ✓ The one chain behind most of it 贯穿大部分内容的那条链 Five of the six calculation patterns are the same move in disguise: set Qd = Qs for P*, Q* - point elasticity + CS / PS as triangles - impose a policy - deadweight loss. Learn it once on P1 and you can re- run it on a tax, a floor, an externality or a monopoly with the numbers swapped. 六种计算套路里有五种是同一招的变装:令 Qd =Qs 求 P *、 Q*→ 点弹性 → CS/ PS 作为三角形→施 加政策→无谓损失。在第1页学会一次,就能换上数 字在税、价格下限、外部性或垄断上重跑一遍。 i Difficulty & marks shown on each card 每张卡片都标注难度与分值 Marks track the real review-session allocations (e. g. the signature chain is marked 3+3+3+3+3 = 15). Use them to pace yourself against the clock. 分值对应真实复习课的分配(例如标志性的链条按 3+3+3+3+3=15 计分)。用它来对着时钟掌握节奏。 AskSia Library · ECON10004 · 双语 Bilingual
• Nash equilibrium（纳什均衡）：每个人都在对对方“最优反应”，没人能单方面偏离获益（稳定但未必有效率）。[2]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf重复博弈与合作 If the game is played once, defection wins and cooperation is doomed. But oligopolists meet repeatedly. With an indefinite horizon, a firm can sustain the cooperative price by threatening to punish a cheater - for example, matching any price cut forever after. If the long-run loss from triggering that price war exceeds the one-off gain from cheating, cooperation can hold. This is how some collusion survives in practice, and why competition law watches repeated-interaction industries closely. 若博弈只玩一次,背叛取胜,合作注定失败。但寡头之间反 复相遇。在无限期视角下,企业可以靠威胁惩罚作弊者来维 持合作价 -- 例如从此永远跟降。若触发价格战的长期损失 超过作弊的一次性收益,合作就能维持。这就是现实中部分 合谋得以存续的原因,也是竞争法密切关注反复互动行业的 原因。 AskSia Library · ECON10004 · 双语 Bilingual i Recap - Chapter 12 in six lines 回顾 -- 第12章六行速记 (1) Game theory handles strategic settings (oligopoly) where your payoff depends on others' choices. (2) Read the payoff matrix: row payoff first, column second. (3) A dominant strategy is best regardless of the rival; play it. (4) A Nash equilibrium is where each best-responds - no one deviates alone (stable, not necessarily efficient). (5) The prisoner's dilemma: individually rational - collectively bad; both confess / both compete. (6) Cartels are unstable - each member gains by cheating; only repeated play with credible punishment can sustain cooperation. (1) 博弈论处理策略性情境(寡头),你的收益取决于他人的选择。(2)读收益矩阵:行收益在前,列收益在后。(3)占优 策略是无论对手怎样都最优的;打它。(4)纳什均衡是各自做最优反应 -- 没人单独偏离(稳定,未必有效)。(5)囚徒困 境:个体理性→集体糟糕;双双认罪/双双竞争。(6)卡特尔不稳定 -- 每个成员靠作弊获益;只有带可信惩罚的反复博 弈才能维持合作。 AskSia Library · ECON10004 · 双语 Bilingual CH 13 . PRACTICE P1 - CHAPTER 13 . PRACTICE BANK DRILL TO EXAM STANDARD Drill the exam, with full solutions 刷考题,附完整解答 Six graded problems in the real review-session style - worked end to end 六道分级题,真实复习课风格 -- 全程解答 These are exam-style problems, built on the real review-session and tutorial templates: multi-part calculation, a graph to draw, and a MCQ set. Every number is verified against this subject's own worked solutions. Treat each one as the real thing first; read the worked answer second. 这些是考试题型的习题,依据真实的复习课与习题课模板编排:多问计算、需作图的题、以及一组选择题。每个数字都已对照 本科目自己的标准解答核验。请先把每道题当作真考来做,之后再看解析。 - ★ How to use this bank 如何使用这个题库 Cover the solution. Work each problem on paper before you read a single line of the answer - recognition is not recall. Budget ~1 minute per mark. A 15-mark problem is a 15-minute problem; if you stall, move on and return. Always draw and fully label the graph - axes, both curves, equilibrium, and the shaded CS / PS / DWL. Graph marks are the easiest marks in the paper. Reconcile at the end: CS + PS + revenue + DWL must add back to the original total surplus, every time. 盖住答案。读到答案的任何一行之前,先在纸上把每 道题做出来 -- 认得出不等于答得出。每分预算约1 分钟。一道15分的题就是15 分钟的题;卡住了就跳 过、稍后回来。永远画出并完整标注图形 -- 坐标 轴、两条曲线、均衡点,以及涂好阴影的 CS/ PS / DWL。图形分是全卷最容易拿的分。最后做对账:CS + PS+ 收入 + DWL 每次都必须加回到原始的社会总 剩余。 ✓ The one chain behind most of it 贯穿大部分内容的那条链 Five of the six calculation patterns are the same move in disguise: set Qd = Qs for P*, Q* - point elasticity + CS / PS as triangles - impose a policy - deadweight loss. Learn it once on P1 and you can re- run it on a tax, a floor, an externality or a monopoly with the numbers swapped. 六种计算套路里有五种是同一招的变装:令 Qd =Qs 求 P *、 Q*→ 点弹性 → CS/ PS 作为三角形→施 加政策→无谓损失。在第1页学会一次,就能换上数 字在税、价格下限、外部性或垄断上重跑一遍。 i Difficulty & marks shown on each card 每张卡片都标注难度与分值 Marks track the real review-session allocations (e. g. the signature chain is marked 3+3+3+3+3 = 15). Use them to pace yourself against the clock. 分值对应真实复习课的分配(例如标志性的链条按 3+3+3+3+3=15 计分)。用它来对着时钟掌握节奏。 AskSia Library · ECON10004 · 双语 Bilingual
• prisoner’s dilemma（囚徒困境）：个体理性导致集体更糟的结果；卡特尔/合谋不稳定，成员都有作弊动机。[2]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf重复博弈与合作 If the game is played once, defection wins and cooperation is doomed. But oligopolists meet repeatedly. With an indefinite horizon, a firm can sustain the cooperative price by threatening to punish a cheater - for example, matching any price cut forever after. If the long-run loss from triggering that price war exceeds the one-off gain from cheating, cooperation can hold. This is how some collusion survives in practice, and why competition law watches repeated-interaction industries closely. 若博弈只玩一次,背叛取胜,合作注定失败。但寡头之间反 复相遇。在无限期视角下,企业可以靠威胁惩罚作弊者来维 持合作价 -- 例如从此永远跟降。若触发价格战的长期损失 超过作弊的一次性收益,合作就能维持。这就是现实中部分 合谋得以存续的原因,也是竞争法密切关注反复互动行业的 原因。 AskSia Library · ECON10004 · 双语 Bilingual i Recap - Chapter 12 in six lines 回顾 -- 第12章六行速记 (1) Game theory handles strategic settings (oligopoly) where your payoff depends on others' choices. (2) Read the payoff matrix: row payoff first, column second. (3) A dominant strategy is best regardless of the rival; play it. (4) A Nash equilibrium is where each best-responds - no one deviates alone (stable, not necessarily efficient). (5) The prisoner's dilemma: individually rational - collectively bad; both confess / both compete. (6) Cartels are unstable - each member gains by cheating; only repeated play with credible punishment can sustain cooperation. (1) 博弈论处理策略性情境(寡头),你的收益取决于他人的选择。(2)读收益矩阵:行收益在前,列收益在后。(3)占优 策略是无论对手怎样都最优的;打它。(4)纳什均衡是各自做最优反应 -- 没人单独偏离(稳定,未必有效)。(5)囚徒困 境:个体理性→集体糟糕;双双认罪/双双竞争。(6)卡特尔不稳定 -- 每个成员靠作弊获益;只有带可信惩罚的反复博 弈才能维持合作。 AskSia Library · ECON10004 · 双语 Bilingual CH 13 . PRACTICE P1 - CHAPTER 13 . PRACTICE BANK DRILL TO EXAM STANDARD Drill the exam, with full solutions 刷考题,附完整解答 Six graded problems in the real review-session style - worked end to end 六道分级题,真实复习课风格 -- 全程解答 These are exam-style problems, built on the real review-session and tutorial templates: multi-part calculation, a graph to draw, and a MCQ set. Every number is verified against this subject's own worked solutions. Treat each one as the real thing first; read the worked answer second. 这些是考试题型的习题,依据真实的复习课与习题课模板编排:多问计算、需作图的题、以及一组选择题。每个数字都已对照 本科目自己的标准解答核验。请先把每道题当作真考来做,之后再看解析。 - ★ How to use this bank 如何使用这个题库 Cover the solution. Work each problem on paper before you read a single line of the answer - recognition is not recall. Budget ~1 minute per mark. A 15-mark problem is a 15-minute problem; if you stall, move on and return. Always draw and fully label the graph - axes, both curves, equilibrium, and the shaded CS / PS / DWL. Graph marks are the easiest marks in the paper. Reconcile at the end: CS + PS + revenue + DWL must add back to the original total surplus, every time. 盖住答案。读到答案的任何一行之前,先在纸上把每 道题做出来 -- 认得出不等于答得出。每分预算约1 分钟。一道15分的题就是15 分钟的题;卡住了就跳 过、稍后回来。永远画出并完整标注图形 -- 坐标 轴、两条曲线、均衡点,以及涂好阴影的 CS/ PS / DWL。图形分是全卷最容易拿的分。最后做对账:CS + PS+ 收入 + DWL 每次都必须加回到原始的社会总 剩余。 ✓ The one chain behind most of it 贯穿大部分内容的那条链 Five of the six calculation patterns are the same move in disguise: set Qd = Qs for P*, Q* - point elasticity + CS / PS as triangles - impose a policy - deadweight loss. Learn it once on P1 and you can re- run it on a tax, a floor, an externality or a monopoly with the numbers swapped. 六种计算套路里有五种是同一招的变装:令 Qd =Qs 求 P *、 Q*→ 点弹性 → CS/ PS 作为三角形→施 加政策→无谓损失。在第1页学会一次,就能换上数 字在税、价格下限、外部性或垄断上重跑一遍。 i Difficulty & marks shown on each card 每张卡片都标注难度与分值 Marks track the real review-session allocations (e. g. the signature chain is marked 3+3+3+3+3 = 15). Use them to pace yourself against the clock. 分值对应真实复习课的分配(例如标志性的链条按 3+3+3+3+3=15 计分)。用它来对着时钟掌握节奏。 AskSia Library · ECON10004 · 双语 Bilingual
• 机会成本 opportunity cost（超级高频概念题）
  • 定义：次优选择的价值（你为当前选择放弃的“最好那个替代方案”），不是你没做所有事的总和，也不一定等于标价。[6]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf14 Exam-morning page clearing the hurdle → i Why this order 为何按此顺序 The book follows the lecture arc: build the market model (Ch 1-4), use it to analyse policy and trade (Ch 5-6 - the most-tested calculation chain), open up the firm and market structures (Ch 7-10), then handle market failure and strategy (Ch 11-12). Part 5 turns it into marks with a graded practice bank. 本书沿讲课脉络展开:先搭建市场模型(第1-4章),用它分析政策与贸易(第5-6章 -- 考得最多的计算链),再展开 企业与市场结构(第7-10章),最后处理市场失灵与策略(第11-12章)。第五部分用一个分级练习题库把这些转化为分 数。 AskSia Library . ECON10004 . XXia Bilingual CH 1 . THINKING FOUNDATIONS CHAPTER 1 The economic way of thinking 经济学的思维方式 Scarcity, trade-offs, and the cost of everything you choose 稀缺、取舍与每个选择的代价 Economics is not about money. It is a way of reasoning about choice under scarcity - and almost every mark in this subject rewards that reasoning applied to a diagram or a number. Master the four moves on these pages (opportunity cost, the frontier, comparative advantage, the margin) and the rest of the course is the same logic with curves attached. 经济学不是关于钱的。它是一种在稀缺条件下对选择进行推理的方式 -- 而本科目几乎每一分都奖励把这种推理应用到图或数 字上。掌握这几页里的四个动作(机会成本、边界、比较优势、边际),课程其余部分就是同一套逻辑再挂上曲线。 ★ What the exam asks here 这里考试问什么 Early questions are concept checks dressed as MCQ and true/false: spot the opportunity cost of a choice, read a point as efficient / inefficient / unattainable on a PPF, and identify who holds comparative advantage from an output table. The trap is always the same - confusing what you spent with what you gave up. 前面的题是披着选择题和判断题外衣的概念检查:找出某选择的机会成本(opportunity cost),判断 PPF(生产可能性 边界)上某点是有效/无效/不可达,并从产出表中辨认谁拥有比较优势(comparative advantage)。陷阱永远一样 把你花掉的当成你放弃的。 1. 1 Scarcity & the economic problem 1. 1 稀缺与经济问题 Wants are unlimited; resources (time, labour, capital, land) are finite. That gap is scarcity, and it forces choice. Every choice to do one thing is simultaneously a choice not to do something else. Economics studies how people, firms and societies allocate scarce resources among competing uses - and the central tool for valuing any choice is its opportunity cost. 欲望无限;资源(时间、劳动、资本、土地)有限。这道缺口就是稀缺(scarcity),它逼出选择。每一次选择做某事,同时 就是选择不做另一件事。经济学研究人、厂商与社会如何在相互竞争的用途间配置稀缺资源 -- 而评估任何选择的核心工具, 就是它的机会成本(opportunity cost)。 1. 2 Opportunity cost 1. 2 机会成本 The opportunity cost of a choice is the value of the next-best forgone alternative - the single best thing you gave up to get what you chose. It is not the sum of everything you didn't do, and it is not the dollar price on the tag. Often the most important cost is time. 一个选择的机会成本(opportunity cost)是放弃的次优选择的价值 -- 你为得到所选之物而放弃的那个最好的东西。它不是 你没做的所有事之总和,也不是标价牌上的金额。最重要的成本往往是时间。 DEFINITION opportunity cost = value of the next-best alternative forgone AskSia Library · ECON10004 · 双语 Bilingual
• 选择题技巧：用“排除法”，不要只靠眼熟
  • 错选项经常是“真概念放错位置”（如把 total 当 marginal、把公共资源说成公共物品等）。能说出每个干扰项“其实在描述什么”，答案就稳。[7]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf- 选(a)的原因:弹性较小的一方承担更多 -- 它无法走开。(b)法定纳税方与经济税负归宿无关。(c)五五分摊需要弹性相等。 (d) 政府收的是税款,不承担税负。 - Q5 MCQ competition vs monopoly rule Which output rule is correct? 哪条产量法则是正确的? (a) Competitive firm: P = MC; monopolist: MR = MC - correct (b) Both produce where P = MC (c) Competitive firm: MR = MC; monopolist: P = MC (d) Both produce where MR = MC and P = MR Why (a) : a price-taker has P = MR, so P = MC; a monopolist faces MR < P, sets MR = MC then prices off demand. (b)/(c) swap the rules. (d) P = MR only holds under competition. 选(a)的原因:价格接受者 P=MR,故 P= MC;垄断者面对 MR <P,先令 MR= MC 再到需求曲线定价。(b)/(c)把法则 弄反了。(d)P = MR仅在竞争下成立。 Pigouvian tax & public goods 06 MCQ Which statement is correct? 哪条陈述是正确的? (a) A Pigouvian tax equals the marginal external cost; a public good is non-rival and non- excludable - correct (b) A Pigouvian tax equals the total external cost (c) A public good is rival but non-excludable (d) A public good is excludable but non-rival AskSia Library · ECON10004 · 双语 Bilingual - Why (a): the optimal corrective tax = the marginal external cost, and a pure public good is both non- rival (my use does not reduce yours) and non-excludable (cannot keep non-payers out). (b) uses total, not marginal. (c) describes a common resource. (d) describes a club good. 选(a)的原因:最优矫正税 = 边际外部成本,而纯公共物品既非竞争性(我用了不减少你用)又非排他性(无法把不付费者 挡在外)。(b)用了总额而非边际。(c)描述的是公共资源。(d)描述的是俱乐部物品。 ✓ MCQ technique - eliminate, don't just recognise 选择题技巧 -- 排除法,别只靠认得 Each wrong option here is a real concept in the wrong slot: a shift instead of a movement, producer surplus labelled as consumer surplus, total external cost instead of marginal, a common resource called a public good. If you can name what each distractor actually describes, the answer is unambiguous - and you have revised four concepts per question. 这里每个错误选项都是放错位置的真实概念:把移动说成沿线变动、把生产者剩余标成消费者剩余、把总外部成本当成 边际、把公共资源叫成公共物品。如果你能说出每个干扰项实际描述的是什么,答案就毫不含糊 -- 而且你每道题复习 了四个概念。 AskSia Library · ECON10004 · 双语 Bilingual CH 14 . EXAM MORNING - CHAPTER 14 . EXAM MORNING CLEARING THE HURDLE If you remember nothing else 其余都忘也记住这些

4）“作图分 = 最稳的救命分”（你要当成必拿）

• 任何大题（甚至题目没要求）都建议画图：
  • 坐标轴命名；两条曲线都画；均衡点标出；$CS/PS/DWL$ 涂阴影并标注。[3]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf坐标轴命名,两条曲线都画,均衡点标出,CS/ PS / DWL 涂阴影并标注。图形分是全卷最容易拿的分,绝 不会因算术失误而丢。即便题目没明确要求,也要画 图。 ~1 min PER MARK - PACE IT 每分一速 · 把控节奏 1st DO YOUR STRONGEST TOPICS FIRST 先做你最拿手的题 50% EXAM IS A HURDLE TO PASS 考试是一道及格线 ▰ BANK GRAPH + DEFINITION MARKS FIRST 先攒下作图分与定义分 ! Pace and pick your order 把控节奏、选好做题顺序 Budget ~1 minute per mark and start with the topics you know cold - bank the certain marks before the clock pressure hits. If a calculation stalls, still draw the graph and state the rule: partial method earns partial marks. Remember the exam is 50% of your grade and a hurdle - secure the graph and definition marks first, then reach for the rest. 每分预算约1分钟,从你最有把握的主题开始 -- 在时间压力袭来前先把稳拿的分收入囊中。若计算卡住,仍要画图并 陈述法则:部分方法得部分分。记住考试占总成绩50% 且是及格线 -- 先拿稳图形分和定义分,再去攻其余的。 Set Qd = Qs. Find the wedge. Shade the triangle. Label everything. You have drilled this - walk in and do it. 令 Qd=Qs。找出税楔。给三角涂阴影。把一切都标注清楚。你已经反复演练过 -- 走进考场把它做出来。 EXAM MORNING . ECON10004 AskSia Library · ECON10004 · 双语 Bilingual AskSia Library A+ COURSE PLAYBOOK FACULTY OF BUSINESS & ECONOMICS SEMESTER 1 . 2026 THE COMPLETE EXAM BIBLE Introductory Microeconomics 微观经济学导论 ONE SUBJECT · EVERY GRAPH, EVERY MODEL, EVERY MARK. 一门课 · 每张图、每个模型、每一分都拿下 ECON10004 . UNIVERSITY OF MELBOURNE 中英双语版 · BILINGUAL EDITION 英文主讲,中文随行 一 考试要点与术语保留英文原词 Built from this subject's own lecture slides, tutorial questions, weekly quizzes and exam- revision sessions. Teaches each model from first principles, draws every diagram, then drills it to exam standard - because the final exam is 50% of your grade and a hurdle. For personal study Not affiliated with or endorsed by the University of Melbourne takedowns@asksia. ai PREFACE HOW TO USE THIS BOOK Three students, one book 三个学生,一本书 Wherever you are right now, start here 无论你现在在哪,从这里开始[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
• 书里直说：图形分是全卷最容易拿的分，不会因为你算术滑了一下就全没。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.

5）用“signature chain”做一遍：你就知道大题怎么写（按评分点拿分）

• 题干（书里给的 15 分标志题）：
  • $Q_D=100-5P,;Q_S=5P$，再征单位税 $t=$2$，要求均衡、弹性、剩余、税后价格/数量/税收/DWL，并画图。[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
• (a) 均衡（3分）
  • $100-5P=5P\Rightarrow 100=10P\Rightarrow P^*=10$
  • $Q^*=5\times 10=50$ 。[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
• (b) 点弹性（3分）
  • $E_d=(-5)\times(10/50)=-1$
  • $E_s=(5)\times(10/50)=+1$
  • 绝对值相等 ⇒ 税负 50/50。[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
• (c) 税前剩余（3分）
  • choke price：$Q_D=0\Rightarrow 100-5P=0\Rightarrow P=20$
  • $CS=\frac12\times 50\times(20-10)=250$
  • $PS=\frac12\times 50\times(10-0)=250$ 。[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
• (d) 征税后（后面 6 分 + 作图）
  • 税后：买者付 $P_b$、卖者收 $P_s$，且 $P_b=P_s+2$
  • 解得 $P_s=9,;P_b=11,;Q=45$ 。[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
  • 税收：$\text{Revenue}=t\times Q=2\times 45=90$
  • 无谓损失：$DWL=\frac12\times 2\times(50-45)=5$ 。[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
• 你会发现：这题就是你考试里会反复遇到的模板（换个市场、换个数字、换成补贴/地板价/外部性/垄断，本质都在重复链条）。[2]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf重复博弈与合作 If the game is played once, defection wins and cooperation is doomed. But oligopolists meet repeatedly. With an indefinite horizon, a firm can sustain the cooperative price by threatening to punish a cheater - for example, matching any price cut forever after. If the long-run loss from triggering that price war exceeds the one-off gain from cheating, cooperation can hold. This is how some collusion survives in practice, and why competition law watches repeated-interaction industries closely. 若博弈只玩一次,背叛取胜,合作注定失败。但寡头之间反 复相遇。在无限期视角下,企业可以靠威胁惩罚作弊者来维 持合作价 -- 例如从此永远跟降。若触发价格战的长期损失 超过作弊的一次性收益,合作就能维持。这就是现实中部分 合谋得以存续的原因,也是竞争法密切关注反复互动行业的 原因。 AskSia Library · ECON10004 · 双语 Bilingual i Recap - Chapter 12 in six lines 回顾 -- 第12章六行速记 (1) Game theory handles strategic settings (oligopoly) where your payoff depends on others' choices. (2) Read the payoff matrix: row payoff first, column second. (3) A dominant strategy is best regardless of the rival; play it. (4) A Nash equilibrium is where each best-responds - no one deviates alone (stable, not necessarily efficient). (5) The prisoner's dilemma: individually rational - collectively bad; both confess / both compete. (6) Cartels are unstable - each member gains by cheating; only repeated play with credible punishment can sustain cooperation. (1) 博弈论处理策略性情境(寡头),你的收益取决于他人的选择。(2)读收益矩阵:行收益在前,列收益在后。(3)占优 策略是无论对手怎样都最优的;打它。(4)纳什均衡是各自做最优反应 -- 没人单独偏离(稳定,未必有效)。(5)囚徒困 境:个体理性→集体糟糕;双双认罪/双双竞争。(6)卡特尔不稳定 -- 每个成员靠作弊获益;只有带可信惩罚的反复博 弈才能维持合作。 AskSia Library · ECON10004 · 双语 Bilingual CH 13 . PRACTICE P1 - CHAPTER 13 . PRACTICE BANK DRILL TO EXAM STANDARD Drill the exam, with full solutions 刷考题,附完整解答 Six graded problems in the real review-session style - worked end to end 六道分级题,真实复习课风格 -- 全程解答 These are exam-style problems, built on the real review-session and tutorial templates: multi-part calculation, a graph to draw, and a MCQ set. Every number is verified against this subject's own worked solutions. Treat each one as the real thing first; read the worked answer second. 这些是考试题型的习题,依据真实的复习课与习题课模板编排:多问计算、需作图的题、以及一组选择题。每个数字都已对照 本科目自己的标准解答核验。请先把每道题当作真考来做,之后再看解析。 - ★ How to use this bank 如何使用这个题库 Cover the solution. Work each problem on paper before you read a single line of the answer - recognition is not recall. Budget ~1 minute per mark. A 15-mark problem is a 15-minute problem; if you stall, move on and return. Always draw and fully label the graph - axes, both curves, equilibrium, and the shaded CS / PS / DWL. Graph marks are the easiest marks in the paper. Reconcile at the end: CS + PS + revenue + DWL must add back to the original total surplus, every time. 盖住答案。读到答案的任何一行之前,先在纸上把每 道题做出来 -- 认得出不等于答得出。每分预算约1 分钟。一道15分的题就是15 分钟的题;卡住了就跳 过、稍后回来。永远画出并完整标注图形 -- 坐标 轴、两条曲线、均衡点,以及涂好阴影的 CS/ PS / DWL。图形分是全卷最容易拿的分。最后做对账:CS + PS+ 收入 + DWL 每次都必须加回到原始的社会总 剩余。 ✓ The one chain behind most of it 贯穿大部分内容的那条链 Five of the six calculation patterns are the same move in disguise: set Qd = Qs for P*, Q* - point elasticity + CS / PS as triangles - impose a policy - deadweight loss. Learn it once on P1 and you can re- run it on a tax, a floor, an externality or a monopoly with the numbers swapped. 六种计算套路里有五种是同一招的变装:令 Qd =Qs 求 P *、 Q*→ 点弹性 → CS/ PS 作为三角形→施 加政策→无谓损失。在第1页学会一次,就能换上数 字在税、价格下限、外部性或垄断上重跑一遍。 i Difficulty & marks shown on each card 每张卡片都标注难度与分值 Marks track the real review-session allocations (e. g. the signature chain is marked 3+3+3+3+3 = 15). Use them to pace yourself against the clock. 分值对应真实复习课的分配(例如标志性的链条按 3+3+3+3+3=15 计分)。用它来对着时钟掌握节奏。 AskSia Library · ECON10004 · 双语 Bilingual[5]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfFormat Share Multiple choice (definitions & diagrams) ~half Multi-part calculation & short answer ~half Graph-drawing (shade CS/PS/DWL) throughout ✓ The strategy this dictates 由此定下的策略 The whole subject is examinable, but it is procedural: a handful of models - supply & demand, surplus, policy & deadweight loss, costs, competition, monopoly, externalities - applied to fresh numbers and drawn as graphs. The recurring calculation is one chain: find equilibrium - elasticity - surplus - impose a policy - deadweight loss. Master that chain and the graphs, and the exam can't surprise you. This book is ordered to build exactly that. 整门科目都可能考,但它是程式化的:一小撮模型 -- 供求、剩余、政策与无谓损失、成本、竞争、垄 断、外部性 -- 套用新数字并画成图。反复出现的计 算就是一条链:求均衡→弹性→剩余→施加政策 →无谓损失。掌握这条链和那些图,考试就难不倒 你。本书正是按这一目标编排的。 AskSia Library · ECON10004 · 双语 Bilingual CONTENTS - CONTENTS The whole subject, in one ordered book 整门课,一本有序的书 Twelve lecture topics - one exam-ready map 十二讲主题→一张考前地图 Ch Topic Core idea Part 1 . The market model 1 The economic way of thinking scarcity . trade-offs → 2 Demand & supply the core model → 3 Elasticity responsiveness · revenue → 4 Surplus & market efficiency CS . PS . the invisible hand →[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.

6）最后给你一个“临考 7 天游泳圈”（按最能提分的顺序）

• 第 1–2 天：只练 signature chain（至少 10 遍）
  • 目标：看到 $Q_d,Q_s$ 就能条件反射写出：均衡→弹性→剩余→政策→DWL，并且图永远完整。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.[19]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf15 marks . the signature chain P1 CALCULATION + GRAPH A perfectly competitive market has demand and supply 某完全竞争市场的需求与供给为 QD = 100 - 5P Qs = 5P QD = 100 - 5P Qs = 5P (a) Find equilibrium P* and Q *. [3] (b) Point elasticities of demand and supply at equilibrium. [3] (c) Consumer and producer surplus. [3] (d) Impose a per-unit tax t = $2. Find the price buyers pay, the price sellers keep, the new quantity, tax revenue and deadweight loss. [3+3] Draw it. (a) 求均衡 P* 与 Q *。 [3] (b)均衡处需求与供给的点弹性。[3] (c)消费者剩余与生产者剩余。[3] (d)征收每单位税 t= $2。求买方支付价、卖方留存价、新数量、税收收入与无谓损失。[3+3]作图。 WORKED SOLUTION 1 (a) Equilibrium. 100 - 5P = 5P -+ 100 = 10P -+ P* = 10; Q* = 5 x 10 = 50. (a) 均衡。100-5P=5P→100=10P→P *= 10; Q* = 5 x 10 = 50. 2 (b) Point elasticities. Ed = (dQ/dP)(P/Q) = (-5) (10/50) = (-1); Es = (5)(10/50) = (+1). Equal magnitudes - the tax burden splits 50/50. (b)点弹性。Ed =(dQ/dP)(P/Q) =(-5)(10/50) =(-1); Es =(5)(10/50)=(+1)。绝对值相等→税负五五分摊。 3 (c) Surplus. Demand choke price (Qp = 0): P = 20. CS = 1/2 × 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 - 0) = 250. (c) 剩余。 需求窒息价格 (Qp= 0): P= 20。CS=1/2 x 50 x (20 - 10) = 250; PS = 1/2 x 50 x (10 -0) =250. 4 (d) Tax t = $2. Tax on buyers: 100 - 5(Ps + 2) = 5Ps +90 = 10Ps - Ps = 9, so Pb = 11; Q = 5 × 9 =45. (d)征税 t=$2。对买方征税:100-5(Ps + 2)=5Ps → 90=10Ps→Ps=9,故 Pb=11; Q=5×9=45。 - 5 Revenue & DWL. Revenue = t x Q = 2 x 45 = 90; DWL = 1/2 x t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. 税收与 DWL。税收= tx Q = 2×45= 90; DWL=1/2 × t x (Q* - Q) = 1/2 x 2 x (50 - 45) = 5. Price ($) S $11 $9 D Quantity The $2 wedge: buyers pay $11, sellers keep $9, quantity falls 50 - 45. Amber = tax revenue (2 x 45 = 90) ; red = deadweight loss (12 x 2 x 5 = 5). $2 的税楔 (wedge):买方付 $11,卖方留 $9,数量从 50 跌到 45。琥珀色= 税收 (2×45=90);红色=无 谓损失(deadweight loss) (1/2×2×5=5)。 I tax revenue I deadweight loss Welfare table - tax t = $2 Before After
• 第 3 天：政策题专项（税/补贴/上限/下限）
  • 重点背：wedge、incidence 规则、DWL 三角形、以及“法定≠经济归宿”。[16]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfI tax revenue I deadweight loss AskSia Library · ECON10004 · 双语 Bilingual - Deadweight loss = the part of lost CS + PS that nobody captures (the red triangle). 无谓损失 = 损失的 CS+PS 中无人捕获的那部分(红色三 角)。 Tax incidence - who actually bears it 税负归宿 -- 谁真正承担 The statutory payer (whoever writes the cheque) is irrelevant. The economic burden is split by relative elasticity: the side that can least escape - the less elastic (steeper) side - absorbs the larger share of the tax. 法定(statutory)缴款方(写支票的那一方)无关紧要。经济负担按相对弹性分摊:最无法逃脱的一方 -- 弹性较小(较陡)的一方 -- 承担更大份额的税。 INCIDENCE RULE The less-elastic side bears MORE of the tax. Buyer's share * Seller's share = Es + | Eal Intuition: an inelastic side keeps trading even as the price moves against it, so the price moves a long way against it - it can't walk away. An elastic side flees a small price move, so the price barely shifts toward it. Demand for cigarettes is inelastic - smokers (buyers) bear most of a tobacco tax; if supply were the inelastic side, sellers would. 直觉:弹性小的一方即便价格对其不利仍继续交易,所以价格会大幅向其不利方向移动 -- 它走不掉。弹性大的一方一遇小幅 价格变动就逃离,所以价格几乎不向它移动。香烟需求缺乏弹性→烟民(买者)承担烟草税的大部分;若供给是缺乏弹性的 一方,就由卖者承担。 ! Don't confuse statutory with economic incidence 别混淆法定归宿与经济归宿 "The tax is on sellers" tells you nothing about who really pays. A sugar-tax MCQ in the review set hinges on exactly this: the answer is decided by which side is less elastic, not by who hands the money to the tax office. “税征在卖方身上”对真正谁付税毫无说明。复习题库里一道糖税选择题正是卡在这点上:答案由哪一方弹性更小决定, 而非由谁把钱交给税务局决定。 - AskSia Library · ECON10004 · 双语 Bilingual CH 5 . SIGNATURE CHAIN - CHAPTER 5 . THE SIGNATURE WORKED CHAIN MEMORISE THIS Equilibrium - elasticity - surplus - tax - DWL 均衡→弹性→剩余→税收→DWL QD = 100 - SP, Qs = SP, then a $2 per-unit tax QD = 100 -5P,Qs=5P,再加 $2 单位税 This is the exam's most-repeated problem, transcribed from the review sessions (RS4/RS4a Q7) and marked 3+3+3+3+3. Learn the five moves and the numbers fall out cleanly every time. 这是考试最常重复的题目,转录自复习课(RS4/RS4a Q7),按3+3+3+3+3评分。学会这五个动作,数字每次都干净利落 地算出来。 1 Equilibrium. 100 - 5P = 5P -+ 100 = 10P - P* = 10, Q* = 5 x10 = 50. 均衡。100-5P=5P→100=10P→P *= 10, Q *= 5 × 10 = 50. 2 Point elasticities at equilibrium. Ed = (dQ/dP) (P/Q) = (-5)(10/50) = (-1); Es =(5)(10/50) = (+1). Equal magnitudes - the tax splits 50/50. 均衡处的点弹性。Ed =(dQ/dP)(P/Q) = (-5)(10/50) = (-1); Es =(5)(10/50)=(+1)。绝对值相等→ 税负五五分 摊。 3 Surplus before tax. Demand choke price (Qd = 0): P = 20. CS = 1/2 × 50 x (20 -10) = 250; PS = 1/2 ×50 x (10 - 0) = 250. 税前剩余。需求窒息价格(Qd=0): P=20。CS= 1/2× 50 × (20 -10) = 250; PS = 1/2 × 50×(10-0)=250.
• 第 4 天：垄断 + 成本 + 竞争（规则题）
  • 死背：竞争 $P=MC$；垄断 $MR=MC$ 且 $MR=a-2bQ$；shutdown：$P<AVC$。[8]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfSix reminders across the subject - read once, walk in, clear the hurdle 横跨全科的六条提醒 -- 读一遍,进考场,过线 THE THREE CORE FORMULAS 1 . The chain set Qp = Qs - P*, Q *; CS / PS are triangle areas; a tax adds a wedge; DWL = 1/2 x tax x AQ 2 . Elasticity £ = (dQ/dP) (P/Q); inelastic (|E| < 1) - raise price for more total revenue 3 . Monopoly MR = MC for Q, then price off demand; MR = a - 2bQ; P > MC - deadweight loss i 1 . The calculation chain is one method 1 · 计算链是一套通用方法 Almost every multi-part question is the same chain: set QD = Qs for P*, Q *; CS / PS are triangle areas (1/2 × base x height); a tax drives a wedge Pb - Ps = t; and DWL = 1/2 x t x AQ. Reconcile: CS + PS + revenue + DWL must add back to the original surplus. 几乎每道多问题都是同一条链:令 QD = Qs 求 P *、 Q *; CS / PS 是三角形面积(1/2×底×高);税打入 一个楔子 Pb-Ps = t; DWL= 1/2 xt x △Q。对账: CS + PS+ 收入 + DWL 必须加回原始剩余。 ✓ 2 . Elasticity by the point formula 2 · 用点弹性公式求弹性 8 = (dQ/dP)(P/Q). If demand is inelastic (|8| < 1), raise price to raise revenue; if elastic, cut it. Total revenue peaks where |s| = 1. On a tax, the less-elastic side bears more - it cannot walk away. & =(dQ/dP)(P/Q)。若需求缺乏弹性 (le|<1),涨价 提高收益;若富有弹性,则降价。总收益在 ||=1 处 达峰值。征税时,弹性较小的一方承担更多 -- 它走 不开。 § 4 . Monopoly 4 · 垄断 Set MR = MC to find the quantity, then read the price off the demand curve - never off MR. For linear demand P = a - bQ, MR = a - 2bQ (twice the slope). Because P > MC, the monopolist under-produces and creates a deadweight loss. 令 MR= MC 求数量,再从需求曲线读价格 -- 绝不 从 MR 读。对线性需求 P= a -bQ, MR = a -2bQ (斜率两倍)。因为 P> MC,垄断者生产不足,造成 无谓损失。 i 5 . Market failure & externalities 5 · 市场失灵与外部性 A negative externality means SMC > PMC: the market over-produces. The fix is a Pigouvian tax = the marginal external cost (SMC - PMC), which lifts private cost to the social cost and restores the efficient quantity. A public good is non-rival and non- excludable - free-riding - under-provision. 负外部性意味着 SMC >PMC:市场过度生产。解法 是庇古税 = 边际外部成本(SMC - PMC),它把私人 成本抬到社会成本,恢复有效数量。公共物品非竞争 且非排他→ 搭便车 → 供给不足。 AskSia Library · ECON10004 · 双语 Bilingual ✓ 3 . Costs & competition 3 · 成本与竞争 Produce where P = MC. Shut down if P < AVC (can't even cover variable cost). In the long run, free entry drives P to min ATC and economic profit to zero; number of firms = market Q + firm q. 在P=MC 处生产。若 P <AVC 则停业(连可变成 本都覆盖不了)。长期中,自由进入把P逼向 min ATC、经济利润逼向零;企业数=市场 Q÷企业 q。 ★ 6 . ALWAYS draw and fully label the graph 6 · 一定要画图并完整标注 Axes named, both curves drawn, equilibrium marked, and CS / PS / DWL shaded and labelled. Graph marks are the easiest marks in the paper and you cannot lose them to an arithmetic slip. Draw the diagram even when the question doesn't explicitly ask.
• 第 5 天：外部性 + 公共物品（定义 + 步骤题）
  • 死背：公共物品双特征；Pigouvian tax = 边际外部成本；按“市场失灵五步法”写。[7]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf- 选(a)的原因:弹性较小的一方承担更多 -- 它无法走开。(b)法定纳税方与经济税负归宿无关。(c)五五分摊需要弹性相等。 (d) 政府收的是税款,不承担税负。 - Q5 MCQ competition vs monopoly rule Which output rule is correct? 哪条产量法则是正确的? (a) Competitive firm: P = MC; monopolist: MR = MC - correct (b) Both produce where P = MC (c) Competitive firm: MR = MC; monopolist: P = MC (d) Both produce where MR = MC and P = MR Why (a) : a price-taker has P = MR, so P = MC; a monopolist faces MR < P, sets MR = MC then prices off demand. (b)/(c) swap the rules. (d) P = MR only holds under competition. 选(a)的原因:价格接受者 P=MR,故 P= MC;垄断者面对 MR <P,先令 MR= MC 再到需求曲线定价。(b)/(c)把法则 弄反了。(d)P = MR仅在竞争下成立。 Pigouvian tax & public goods 06 MCQ Which statement is correct? 哪条陈述是正确的? (a) A Pigouvian tax equals the marginal external cost; a public good is non-rival and non- excludable - correct (b) A Pigouvian tax equals the total external cost (c) A public good is rival but non-excludable (d) A public good is excludable but non-rival AskSia Library · ECON10004 · 双语 Bilingual - Why (a): the optimal corrective tax = the marginal external cost, and a pure public good is both non- rival (my use does not reduce yours) and non-excludable (cannot keep non-payers out). (b) uses total, not marginal. (c) describes a common resource. (d) describes a club good. 选(a)的原因:最优矫正税 = 边际外部成本,而纯公共物品既非竞争性(我用了不减少你用)又非排他性(无法把不付费者 挡在外)。(b)用了总额而非边际。(c)描述的是公共资源。(d)描述的是俱乐部物品。 ✓ MCQ technique - eliminate, don't just recognise 选择题技巧 -- 排除法,别只靠认得 Each wrong option here is a real concept in the wrong slot: a shift instead of a movement, producer surplus labelled as consumer surplus, total external cost instead of marginal, a common resource called a public good. If you can name what each distractor actually describes, the answer is unambiguous - and you have revised four concepts per question. 这里每个错误选项都是放错位置的真实概念:把移动说成沿线变动、把生产者剩余标成消费者剩余、把总外部成本当成 边际、把公共资源叫成公共物品。如果你能说出每个干扰项实际描述的是什么,答案就毫不含糊 -- 而且你每道题复习 了四个概念。 AskSia Library · ECON10004 · 双语 Bilingual CH 14 . EXAM MORNING - CHAPTER 14 . EXAM MORNING CLEARING THE HURDLE If you remember nothing else 其余都忘也记住这些[13]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdftype / before quality contract used-car "lemons" Moral action / after hazard effort contract risky behaviour once insured Remedies for both internalise the missing information: warranties and certification signal quality; lemon laws and reputation systems penalise hiding it; deductibles and monitoring curb moral hazard. 两类问题的解法都在于把缺失的信息内部化:保修与认证可 传递质量信号;柠檬法和声誉系统惩罚隐瞒;免赔额与监督 则遏制道德风险。 AskSia Library · ECON10004 · 双语 Bilingual ★ Recap - the market-failure exam move 回顾 -市场失灵的考试技巧 (1) Identify the failure - externality (which side, which sign?), public good, common resource, or asymmetric information. (2) Find Q_market from the private curves (PMB = PMC). (3) Find Q* from the social curves (MB = SMC, or SMB = PMC). (4) The DWL is the triangle between Qm and Q*, with height the external cost/benefit. (5) The fix: Pigouvian tax = marginal external cost (negative), subsidy = marginal external benefit (positive); or Coasian bargaining when parties are few and rights are clear; or government provision for public goods. (1) 辨认失灵类型 -- 外部性(哪一侧、什么符号?)、公共物品、公共资源还是信息不对称(asymmetric information)。(2)由私人曲线求 Q_市场(PMB=PMC)。(3)由社会曲线求 Q* (MB = SMC,或 SMB=PMC)。(4) DWL 是 Qm 与 Q* 之间的三角形,高为外部成本/收益。(5)解法:庇古税=边际外部成本(负外部性),补贴= 边际 外部收益(正外部性);或当事方少、产权清晰时用科斯式谈判;或公共物品由政府提供。 AskSia Library · ECON10004 · 双语 Bilingual CH 12 . GAME THEORY - CHAPTER 12 . GAME THEORY STRATEGY When your best move depends on theirs 最优应对取决于对方时 Payoff matrix . dominant strategy . Nash equilibrium . the prisoner's dilemma 支付矩阵 · 占优策略 · 纳什均衡· 囚徒困境 In perfect competition and monopoly a firm could ignore individual rivals. In an oligopoly - a few large firms - that breaks down: each firm's best move depends on what the others do. Game theory is the toolkit for these strategic situations, and its central result is unsettling: rational players, each acting in self-interest, can land everyone in an outcome they all dislike. 在完全竞争(perfect competition) 和垄断(monopoly)中,企业可以不理会单个对手。但在寡头垄断(oligopoly,少数几 家大企业)里,这一点崩溃了:每家企业的最佳行动都取决于其他企业怎么做。博弈论(game theory)正是分析这类策略性 情形的工具,而它的核心结论令人不安:理性的参与者各自追求自身利益,却可能把所有人推入一个谁都不喜欢的结局。 ★ What the exam does with this 考试如何考这一点 You will be handed a 2×2 payoff matrix and asked to find the equilibrium. The reliable method: (1) for each player, check whether one strategy beats the other no matter what the rival does - that is a dominant strategy. (2) The cell where each player is best-responding to the other is the Nash equilibrium - no one can gain by deviating alone. Be ready to identify it as a prisoner's dilemma and explain why the firms can't sustain the cooperative outcome.
• 第 6 天：贸易 + 关税（图形题）
  • 重点：关税一定有 两个 $DWL$ 三角形；按“trade drill”五步算。[17]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdfNet effect of the tariff — two DWL triangles Why economists prefer a subsidy to a tariff 经济学家为何偏好补贴胜过关税 To raise domestic production by a given amount, a production subsidy distorts only the production side - one DWL triangle. A tariff doing the same job also raises the consumer price, adding the consumption-distortion triangle - two triangles. Same producer gain, but the tariff destroys more total surplus. 要把国内产量提高给定的量,生产补贴只扭曲生产侧 -- 一个DWL三角形。而做同样工作的关税还会抬高消费者价格,添上 消费扭曲三角形 -- 两个三角形。生产者收益相同,但关税毁掉更多社会总剩余。 i Worked - carrot import tariff (RS2-4pm Q2) 例题 -- 胡萝卜进口关税(RS2-4pm Q2) Open economy Qd = 500 - 3P, Qs = P - 100, world price $120. At $120: Qd = 140, Qs = 20-+ imports = 120. Add a $10 tariff - price $130: Qd = 110, Qs = 30 -+ imports = 80. Imports fall by 40 tons - and two small DWL triangles open between the old and new quantities. 开放经济 Qd = 500 - 3P,Qs = P-100,世界价格 $120。在 $120: Qd = 140,Qs = 20→ 进口=120。加征 $10 关税→价格 $130: Qd = 110,Qs = 30→ 进口= 80。进口减少 40 吨 -- 并在新旧数量之间张开两个小的 DWL 三 角形。 ! Count BOTH triangles 两个三角形都要算 On import tariffs the most-missed mark is the second triangle. A tariff # a domestic tax: it distorts both production (too much made at home) and consumption (too little bought). If your tariff diagram shows only one DWL triangle, you have under-counted the welfare loss. 进口关税题里最常丢的分是第二个三角形。关税≠国内税:它同时扭曲生产(国内产太多)和消费(买得太少)。如果 你的关税图只画了一个DWL 三角形,你就少算了福利损失。 AskSia Library · ECON10004 · 双语 Bilingual i Exam move - the trade drill 考试技巧 -- 贸易计算套路 (1) Find the autarky P* from Qd = Qs. (2) Compare Pw: below - import, above - export. (3) At Pw, read Qd and Qs; the gap is imports/exports. (4) CS & PS as triangles against the world-price line. (5) A tariff raises the line by t - recompute imports, add tariff revenue, and shade the two DWL triangles. - (1)由 Qd = Qs 求自给自足 P *。 (2)比较 Pw:低于则进口,高于则出口。(3)在 Pw 处读出 Qd 与 Qs,差额即进口/出 口量。(4)对着世界价格线把 CS与 PS 作为三角形。(5)关税把价格线抬高 t -- 重算进口、加上关税收入,并把两个 DWL 三角形涂阴影。 AskSia Library · ECON10004 · 双语 Bilingual CH 7 . COSTS - CHAPTER 7 . PRODUCTION & COSTS BEHIND SUPPLY What it costs the firm to make the goods 厂商造货的成本 Economic cost . sunk vs fixed vs variable . the production function 经济成本 · 沉没/固定/可变·生产函数 Supply curves do not fall from the sky - they come from a firm's costs. Before we can ask how much should a firm produce, we need to measure cost the way an economist does, sort costs by whether they actually matter for a decision, and see where the familiar U-shaped curves come from. That is this chapter; the next one puts these curves to work. 供给曲线不是凭空掉下来的 -- 它来自厂商的成本。在能问厂商应生产多少之前,我们得用经济学家的方式衡量成本、按是否 真正影响决策对成本归类,并看出那些熟悉的U形曲线从何而来。这就是本章;下一章则让这些曲线发挥作用。 ★ What the exam does with this 考试如何考这一点
• 第 7 天：选择题冲刺
  • 按书里方法：逐个选项说清“它其实是什么概念”，用排除法锁答案。[7]Source: unimelb-econ10004-microeconomics-exam-bible-bilingual.pdf- 选(a)的原因:弹性较小的一方承担更多 -- 它无法走开。(b)法定纳税方与经济税负归宿无关。(c)五五分摊需要弹性相等。 (d) 政府收的是税款,不承担税负。 - Q5 MCQ competition vs monopoly rule Which output rule is correct? 哪条产量法则是正确的? (a) Competitive firm: P = MC; monopolist: MR = MC - correct (b) Both produce where P = MC (c) Competitive firm: MR = MC; monopolist: P = MC (d) Both produce where MR = MC and P = MR Why (a) : a price-taker has P = MR, so P = MC; a monopolist faces MR < P, sets MR = MC then prices off demand. (b)/(c) swap the rules. (d) P = MR only holds under competition. 选(a)的原因:价格接受者 P=MR,故 P= MC;垄断者面对 MR <P,先令 MR= MC 再到需求曲线定价。(b)/(c)把法则 弄反了。(d)P = MR仅在竞争下成立。 Pigouvian tax & public goods 06 MCQ Which statement is correct? 哪条陈述是正确的? (a) A Pigouvian tax equals the marginal external cost; a public good is non-rival and non- excludable - correct (b) A Pigouvian tax equals the total external cost (c) A public good is rival but non-excludable (d) A public good is excludable but non-rival AskSia Library · ECON10004 · 双语 Bilingual - Why (a): the optimal corrective tax = the marginal external cost, and a pure public good is both non- rival (my use does not reduce yours) and non-excludable (cannot keep non-payers out). (b) uses total, not marginal. (c) describes a common resource. (d) describes a club good. 选(a)的原因:最优矫正税 = 边际外部成本,而纯公共物品既非竞争性(我用了不减少你用)又非排他性(无法把不付费者 挡在外)。(b)用了总额而非边际。(c)描述的是公共资源。(d)描述的是俱乐部物品。 ✓ MCQ technique - eliminate, don't just recognise 选择题技巧 -- 排除法,别只靠认得 Each wrong option here is a real concept in the wrong slot: a shift instead of a movement, producer surplus labelled as consumer surplus, total external cost instead of marginal, a common resource called a public good. If you can name what each distractor actually describes, the answer is unambiguous - and you have revised four concepts per question. 这里每个错误选项都是放错位置的真实概念:把移动说成沿线变动、把生产者剩余标成消费者剩余、把总外部成本当成 边际、把公共资源叫成公共物品。如果你能说出每个干扰项实际描述的是什么,答案就毫不含糊 -- 而且你每道题复习 了四个概念。 AskSia Library · ECON10004 · 双语 Bilingual CH 14 . EXAM MORNING - CHAPTER 14 . EXAM MORNING CLEARING THE HURDLE If you remember nothing else 其余都忘也记住这些

如果你愿意，我可以按你们 final 的真实节奏来带你：

• 你告诉我你最慌的是哪块：(A) 税/管制 (B) 垄断 (C) 外部性 (D) 贸易关税 (E) 成本与竞争 (F) 博弈论，我就用这份宝典里的套路给你出一题“同款题”，你做，我帮你按给分点改到能过 hurdle。

（可选）如果你想的话，我也可以把你这门课“你最薄弱的三块 + 你常错的公式点”记住，后面每天按清单帮你刷到考试当天。