Question: On average, 4 customers arrive per hour at a local bank that currently has a single teller. The transaction time per customer varies according to a negative exponential distribution, with a mean of 5 minutes. Using an M/M/1queuing model,

a) What is the probability that a customer will be served immediately without waiting?

b) How long does a customer currently wait in the queue, on average?

c) The bank will add a second teller when a customer’s waiting time in the queue gets to be 6 minutes or longer. How high must the customer arrival rate per hour be to justify a second teller?