Managing Supply Chain and Operations 1st Edition by Thomas Foster ,Scott Sampson,Cynthia Wallin,Scott Webb

Exercise 25

An ATM located on a college campus is able to process, on average, one customer request every 2 minutes. (Assume that the processing times are exponentially distributed and that each person using the ATM makes only one request per visit.) If students arrive at the ATM at the rate of 10 per hour throughout the day, find the following:
a. Percent of time the ATM is busy
b. Probability the ATM is not in use when a student arrives
c. Average number of students waiting to use the ATM
d. Average time a student spends waiting in line to use the ATM
e. Average time spent waiting and using the ATM
f. Average number of students waiting and using the ATM (i.e., the average number of customers in the system)