Richard Muszynski’s Gas and Wash has an automatic car wash, and customers purchasing gas at the station receive a discounted car wash, depending on the number of gallons of gas they buy. The car wash can accommodate one car at a time, and it takes exactly 5 minutes to wash each car. In addition, it is known that the average number of vehicles waiting in the line is 2.

(a) Use Goal Seek and the M/D/1 model to estimate the average arrival rate of vehicles to the car wash.

(b) How long does each vehicle wait in line on average (in minutes)?