每日一练
例题
Question: Consumer surplus
A. Find Marginal Buyer’s WTP (Willingness to Pay) at Q=10.
B. Find Consumer Surplus for P=30.
Suppose P falls to $20. How much will Consumer Surplus increase due to:
C. buyers entering the market
D. existing buyers paying lower price
解析
A. At Q=10, marginal buyer’s WTP (willingness to pay) is $30.
B. Consumer surplus = ½ ×10 × $10 = $50
P falls to $20.
C. Consumer surplus for the additional buyers = ½ ×10 × $10 = $50
D. Increase in Consumer surplus o initial 10 units = 10 × $10 = $100
下面我们为大家准备了一道同类型的题目，请大家一起来试试解答。
Question: Producer Surplus
A. Find Marginal Seller’s cost at Q=10.
B. Find total Producer Surplus for P=$20.
Suppose P rises to $30.
Find the increase in Producer Surplus due to:
C. selling 5 additional units
D. getting a higher price on the initial 10 units
（答案见下方）
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A. At Q=10, marginal cost=$20
B. Producer surplus = ½ × 10 × $20 =$100
P rises to $30.
C. Producer surplus on additional units = ½ × 5 × $10 = $25
D. Increase in Producer surplus on initial 10 units = 10 × $10 = $100
