我用cross elasticity算出e在用MR公式算出也是这个答案

问题如下：

Emma sells homemade cakes in New York. Everyday she can sell 250 cakes with a price of $10. She offers special discount on Mother's day and expected to sell 350 cakes with a discounted price of $8. The marginal revenue per cake she sells from special discount is:

选项：

A.

$3.

B.

$2.

C.

$2.5

解释：

A is correct.

Marginal revenue is the increase in total revenue from selling one more unit of a good. In this case, selling 100 more cakes increase the revenue of $300 (350*$8-250*$10), therefore the marginal revenue is $300/100=$3

考点：边际收益

解析：

首先求得总收益的增加量$300 (350*$8-250*$10)

再求得销售量的增加量100

之后套用公式：边际收益=总收益的增加÷产量的增加

$300/100=$3.