A fast food chain is designing a new location and needs to determine how much driveway space to allow for cars waiting to drive up to the service window. The drive-thru service will have 3 pick-up windows and a single waiting line. At another location in a similar setting, the average service time is 4 minutes per customer and average arrival rate is 36 customers per hour. It is expected that the new location will have similar characteristics. What is the average time that a customer would have to wait in line before being served?
a. 3.9
b. 3.4
c. 4.9
d. 4.3