Michael's Tire Company performs free tire balance and rotation for the life of any tires purchased there on a first-come, first-served basis. One mechanic handles this and can usually complete the job in an average of 20 minutes. Customers arrive at an average rate of two per hour for this service.
a. How long will a customer expect to wait before being served?
b. How long will a customer expect to spend at the shop?
c. How many customers will be waiting, on the average?
d. What is the probability that the mechanic will be idle?"