A Small Popular Restaurant at an Interstate Truck Stop Provides

Multiple Choice

A small popular restaurant at an interstate truck stop provides priority service to truckers. The restaurant has ten tables where customers may be seated. The service time averages 40 minutes once a party is seated. The customer arrival rate is 12 parties per hour, with the parties being equally divided between truckers and non-truckers.
What is the approximate average time in minutes that non-truckers wait to be seated?

A) 2.7
B) 4.5
C) 8.4
D) 13.6
E) 15.8