For the daily output of an industrial operation, let Y1 denote the amount of sales and Y2, the costs, in thousands of dollars. Assume that the density functions for Y1 and Y2 are given by

The daily profit is given by U = Y1 − Y2.

a Find E(U).

b Assuming that Y1 and Y2 are independent, find V(U).

c Would you expect the daily profit to drop below zero very often? Why?