39. A chemical supply company currently has in stock 100 lb of a certain chemical, which it sells to customers in 5-lb lots.

Let X
the number of lots ordered by a randomly chosen customer, and suppose that X has pmf Compute E(X) and V(X). Then compute the expected number of pounds left after the next customer’s order is shipped and the variance of the number of pounds left. [Hint: The number of pounds left is a linear function of X.]