If your reservation price for a pre-cooked meal is $10 and the opportunity cost of the pre-cooked meal is $7, the economic surplus of having a pre-cooked meal equals:

A) $0.7. B) $1.43 C) $3. D) $10. E) $17.

这是我用的清华出的微观经济学原理2版的一个题目,因为我本人是上外的,专业课大多被英语和2外占了,所以不是很清楚该怎么做,老师好象也没有教过,可怜的我需要大家的帮助~~~~~~~~~~