4.43 A notebook computer dealer mounts a new promotional campaign. Purchasers of new computers may, if dissatisfied for any reason, return them within 2 days of purchase and receive a full refund.

The cost to the dealer of such a refund is $100. The dealer estimates that 15% of all purchasers will, indeed, return computers and obtain refunds. Suppose that 50 computers are purchased during the campaign period.

a. Find the mean and standard deviation of the number of these computers that will be returned for refunds.

b. Find the mean and standard deviation of the total refund costs that will accrue as a result of these 50 purchases.