In: Statistics and Probability
A small branch bank has two tellers, one for deposits and one for withdrawals. Customers arrive at each teller’s window with an average rate of 18 customers per hour. (The total customer arrival rate is 36 per hour.) The interarrival times are exponential. The service time of each teller is exponential with a mean of 3 minutes. The bank manager is considering changing the setup to allow each teller to handle both withdrawals and deposits to avoid the situations that arise from time to time when the queue is sizable in front of one teller while the other is idle. However, since the tellers would have to handle both deposits and withdrawals, their efficiency would decrease to a mean service time of 3.2 minutes. Compare the present system with the proposed system with respect to the total average number of customers in the banks and the average time a customer would have to spend in the bank.