Cars Arrive at a Single-Bay Car Wash at an Average

Multiple Choice

Cars arrive at a single-bay car wash at an average of 6 per hour according to the Poisson distribution. The wash time averages 4 minutes with a standard deviation of 1 minute, but the wash time is not defined by any distribution. What is the average number of cars in line?

A) .142
B) .267
C) .283
D) 2.83