A small mail-order business has one telephone line and a facility for call waiting for two additional customers. Orders arrive at the rate of one per minute and each order requires 2 minutes and 30 seconds to take down the particulars. (a) What is the expected number of calls waiting in the queue? What is the mean waiting time in queue? (b) On the average, how many calls will be served per hour? (c) I have just joined the line. On the average, how long will it be before my order is completed?