The parts department of a large automobile dealership has a counter used exclusively for its own service mechanics requesting parts. The length of time between requests can be modelled by an Exponential distribution that has a mean of 5.0 minutes. A parts clerk can handle requests at an average rate of 20 per hour, and this can be modelled by a Poisson distribution. Suppose there are two parts clerks at the counter. Refer to the Table18-4 for Lq values.