Consider a queuing situation involving a single server. Service time is exponentially distributed with an expected value of:
a. 6 min/customer when there is one customer in the system
b. 5 minutes when there are 2 in the system
c. 4 minutes when there are 3 in the system
d. 3 minutes when there are 4 in the system
e. 2 minutes/customer when there are 5 in the system.