The Local Grocery Store Consists of Two Cashiers

Multiple Choice

The local grocery store consists of two cashiers. The customers arrive at the checkout according to the Poisson distribution and the service times are based on negative exponential distribution. The average customer service time is 4 minutes and the average time between the arrivals of successive customers is 3 minutes. Assume that customers equally divide themselves between the two cashiers.
-What is the probability that there are no customers in the grocery store?

A) .166
B) .333
C) .5
D) .667