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Susie · 2023年03月26日

这题给出的解答步骤没明白，老师可否细讲下

  1. CFA I
  2. Economics Analysis

NO.PZ2022071403000039

问题如下：

Question

A power generation company is a monopoly that has very high barriers to entry. The quantity demand (QD) for its product is QD = 800 – 0.25 × P (where P is price). The slope of the marginal revenue curve is closest to:

选项：

A.–0.25. B.–8.00. C.–4.00.

解释：

Solution

B is correct. Solve for P from the quantity demanded:

Q = 800 – 0.25P

P = 3,200 – 4Q

TR = P × Q = 3,200Q – 4Q2

MR = ΔTR/ΔQ = 3,200 – 8Q

Therefore, the slope of the curve is –8.

A is incorrect because it is the slope of the quantity demanded.

C is incorrect because it is the slope of the demand curve (–1/0.25) when P is a function of Q.



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1 个答案

笛子_品职助教 · 2023年03月27日

嗨，从没放弃的小努力你好：


这题给出的解答步骤没明白，老师可否细讲下


Hello，亲爱的同学！


这道题涉及到边际收益这个概念的计算。

MR = ΔTR/ΔQ，也就是每生产1个产品的收益。


从上述看出：

边际收益MR = TR对Q的求导

而TR = P*Q


回到本题的条件

我们已知:Q = 800 – 0.25P，进行变化，把P放到左边。

P = 3,200 – 4Q

TR = P*Q = 3200Q -4Q^2


我们只需对上面这个公式进行求导就可以。


求导有导数法则来决定：


我们用以上红框里的导数计算法则可以计算出：

MR = TR对Q求导 = 3,200 – 8Q


3200 - 8Q 这个表达式，Q前的系数是-8，因此斜率是-8.

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努力的时光都是限量版，加油！

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NO.PZ2022071403000039 问题如下 Question A power generation company is a monopoly thhvery high barriers to entry. The quantity man(Q for its prois Q= 800 – 0.25 × P (where P is price). The slope of the marginrevenue curve is closest to: A.–0.25. B.–8.00. C.–4.00. SolutionB is correct. Solve for P from the quantity manQ = 800 – 0.25PP = 3,200 – 4QTR = P × Q = 3,200Q – 4Q2MR = ΔTR/ΔQ = 3,200 – 8QTherefore, the slope of the curve is –8.A is incorrebecause it is the slope of the quantity manC is incorrebecause it is the slope of the mancurve (–1/0.25) when P is a function of Q.

2023-03-15 09:35 1 · 回答

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2023-03-15 09:25 1 · 回答