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.
On average, how much longer in minutes do parties of non-truckers spend in the system, compared to parties of truckers?

A) 4.
B) 7.
C) 11.
D) 15.
E) It is impossible to determine without more information.