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一只可爱的猪 · 2020年03月17日

问一道题：NO.PZ2018062003000067

  1. CFA I
  2. Economics Analysis

问题如下：

For a market of perfect competition, the demand schedule is defined as P = 165– 3Q (for Q ≤ 55). For each company in the long-run, the total cost is given by: 125 + Q + 5Q2, the average cost is given by: 125/Q + 1 + 5Q, the marginal cost is given by: 1 + 10Q. At which of the following price, new competitors are most likely to enter?

选项：

A.

135.

B.

51.

C.

45.

解释：

B is correct

In a perfectly competitive market, for each company in the long-run, only when MC = AC = P, would the equilibrium be expected.

we can draw the equation:

MC=AC: 1 + 10Q = 125/Q + 1 + 5Q, Q=5.

At that time, P=MC= 1 + 10Q = 51

If the price is higher than 51, new competitors will enter for economic profits .

考点：完全竞争市场

解析：在完全竞争市场中，存在条件 MC = AC = P，

联立MC=AC: 1 + 10Q = 125/Q + 1 + 5Q, Q=5.，

解得：P=MC= 1 + 10Q = 51。

注意到，之所以不用需求函数 P = 165– 3Q参与联立是因为这里给的是整个市场的需求函数，而非单个厂商的 。但是题目给定的MC,AC都是单个厂商的关系式，所以整个市场的需求函数与它们并不匹配，不能参与联立。

为什么MC=AC?

MR=MC

MR=P

但是为什么等于AC?

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1 个答案

源_品职助教 · 2020年03月17日

嗨，从没放弃的小努力你好：


这道题出道的不太好。

可能是市场长期均衡，然后企业不赚不亏（没有盈利也没有亏损），那么P=AC。

大概知道这么个意思就可以了。


-------------------------------
努力的时光都是限量版，加油！


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