Question: Willow Brook National Bank operates a drive up teller window that allows customers to complete bank transactions without getting out of their cars. On weekday mornings arrivals to the drive up teller window occur at random, with an arrival rate of 24 customers per hour or 0.4 customers per minute.

a. What is the mean or expected number of customers that will arrive in a five minute period?
b. Assume that the Poisson probability distribution can be used to describe the arrival process. Use the arrivate rate in part (a) and compute the probabilities that exactly 0,1,2, and 3 customers will arrive during a five minute period.

c. delays are expected if more than three customers arrive during any five minute period. What is the probability that delays will occur?