Consider an ATM of a bank located at a metro station. Only one
person can use the machine, so a queue forms when two or more
customers are present. The metro station is limited in size and can
hold only five people. When there are more than five people,
arriving customers will not enter the queue. Statistics indicates
that the average time between arrivals is 30 seconds, whereas the
time for service averages 24 seconds. Both times follow exponential
distribution....