Response to the following problem:
Customers arrive at Home stake Bank between the hours of 10 A.M. and 11 A.M. according to a Poisson distribution at a mean rate of 40 per hour. During the period from 10 A.M. to 11 A.M. the bank has 3 tellers working. The average time a teller spends with a customer is 3 minutes, and service time follows an exponential distribution.
What is the average time a customer will spend waiting in line before seeing a teller?