On average, 100 customers arrive per hour at Gotham City Bank. It takes a teller an average of 2 minutes to serve a customer. Interarrival and service times are exponentially distributed. The bank currently has 4 tellers working. The bank manager wants to compare the following two systems with regard to the average number of customers present in the bank and the probability that a customer will spend more than 8 minutes in line.

■ System 1: Each teller has his or her own line (and no moving between lines is permitted). Arriving customers are equally likely to choose any teller.

■ 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?