Nervous Cruise Vacationers Besiege Tatiana, Their Excursion Coordinator, at the Port

Nervous cruise vacationers besiege Tatiana, their excursion coordinator, at the Port of Cozumel when they realize that all water excursions have been cancelled for no reason in particular. It takes her 2.5 minutes to find the customers an alternative excursion activity and customers cluster around her at the rate of 20 per hour. About how long does a customer spend waiting in line and receiving her valuable service if the service times are exponentially distributed and the arrivals follow a Poisson distribution?

A) 12.5 minutes
B) 4.17 minutes
C) 5 minutes
D) 15 minutes