Customers Arrive at a Suburban Ticket Outlet at the Rate

Multiple Choice

Customers arrive at a suburban ticket outlet at the rate of 14 per hour on Monday mornings (exponential interarrival times) . Selling the tickets and providing general information takes an average of 3 minutes per customer, and varies exponentially. There is 1 ticket agent on duty on Mondays.
How many minutes does the average customer spend in the system?

A) 7.
B) 8.
C) 9.
D) 10.
E) 11.