Repair calls are handled by one repairman at a photocopy shop. Repair time, including travel time, is exponentially distributed, with a mean of 1.3 hours per call. Requests for copier repairs come in at a mean rate of five per eight-hour day (assume Poisson). Determine:
a. The average number of customers awaiting repairs.
b. The average number of minutes that customers await repairs.
c. The amount of time during an eight-hour day that the repairman is not out on a call.