1. During the hours from 7 to 9 p.m., customers at the Crevice Factory Outlet arrive at the checkout desk at the rate of one every two minutes. It takes an average of 3 minutes to check out a customer. Although there is no limit to the length of the waiting line, it is the store policy that the waiting line should not exceed one customer, on an average. The head office sends out representatives unannounced from time to time to monitor the store's operations, and one of the things they observe is the waiting line.

a. What is the average service rate per minute?

b. How many clerks should be on duty at this time?

c. With this number of clerks, how long does it take the average customer to check out?