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

Multiple Choice

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 many customers are waiting in line to receive her valuable service if the service times are exponentially distributed and the arrivals follow a Poisson distribution?

A) 2.78
B) 4.17
C) 3.25
D) 5.00