The cafeteria line in the university student center is a self-serve facility in which students select the items they want and then form a single line to pay the cashier. Students arrive at a rate of about four per minute according to a Poisson distribution. The single cashier takes about 12 seconds per customer, following a negative exponential distribution.

A) The average number of students in the system is ____

students

B) A second cashier is added and works at the same pace. Assume customers wait in a single line and go to the first available cashier.

The probability that the two server system is empty is _____

C) The average waiting time for the two server system is _______

D) The average number of students in the queue for the two server system is

______

E) The average number of students in the two server system is _______

students