The manager of a bank must determine how many tellers should work on Mondays. On average, 2 customers per minute arrive at the bank, and it takes a teller 2 minutes, on average, to complete a customer's transaction. Both interarrival and service times follow exponential distribution. There is a single queue, and the arriving customers take a number which indicates their place in the queue. Whenever a teller becomes available, the customer having the smallest number moves to the service encounter. Assume that no customers balk or renege. a. If the manager thinks that expected customer waiting time in the queue should not exceed 5 minutes, determine how many tellers are needed