In the service department of the Glenn-Mark Auto Agency, mechanics requiring parts for auto repair or service present their request forms at the part department counter. The parts clerk fills a request while the mechanic waits. Mechanics arrive in a random (Poisson) fashion at the rate of 32/hr., and a clerk can fill requests at the rate of 20/hr. Given the cost for a mechanic is $70/hr., and the cost for a clerk is $25/hr.

Required:
a. Determine the optimum number of clerks to staff the counter.
b. How many mechanics are waiting in line on average?
c. What is the optimum number of clerks to staff the counter?