Layson Roofing Inc. installs shingle roofs on new and old homes in Arkansas.

Prospective customers request the service randomly at the rate of 6 jobs per 30-day month and are placed on a waiting list to be processed on a FCFS basis. Homes sizes vary, but it is fairly reasonable to assume that the roof areas are uniformly distributed between 120 and 360 squares. The work crew can usually complete 60 squares a day.

Determine the following:

(a) Layson’s average backlog of roofing jobs.

(b) The average time a customer waits until a roofing job is completed.

(c) If the work crew is increased to the point where they can complete 100 squares a day, how will this affect the average time until a job is completed?