Customers arrive to a thrift bank branch according to a Poisson distribution at a mean rate 50 customers per hour. The bank uses a single line, multiple-teller operations; and each person at the head of the line goes to the first available teller. A customer's transaction time at any windows averages 3 minutes and is exponentially distributed. The bank manager does not want a customer's average waiting time in the queue to be more than 2 minutes.
a- State the applicable queuing model.
b- What is the minimum number of tellers required for there to exist a steady state for this queuing system?
c- What is the minimum number of tellers required to meet the 2-minute criterion?