A copier repair person is responsible for servicing the copying machines for seven companies in a local area. Repair calls come in at an average of one call every other day. The arrival rate follows the Poisson distribution. Average service time per call, including travel time, is exponentially distributed, with a mean of two hours. The repair person works an eight-hour day.
(a) On average, how many hours per day is the repair person involved with service calls?
(b) How many hours, on average, does a customer wait for the repair person to arrive after making a call?
(c) What is the probability that more than two machines are out of service at the same time?