12 An average of 100 customers per hour arrive at Gotham City Bank. It takes a teller an average of 2 minutes to serve a customer. Interarrival and service times are exponential.

The bank currently has four tellers working. The bank manager wants to compare the following two systems with regard to average number of customers present in the bank and the probability that a customer will spend more than 8 minutes in the bank:

System 1 Each teller has her own line, and no jockeying between lines is permitted.

System 2 All customers wait in a single line for the first available teller.

If you were the bank manager, which system would you prefer?