=a. You ask Mark to describe the demand and service rate. He tells you that calls are randomly received by the call center and that the center receives an average of 70 calls per hour.

The computer system installed to answer and hold the calls is so advanced that its capacity far exceeds the demand.

Because the nature of a call is random, the time required to process a call is random, where the time frequently is small but occasionally can be much longer. On average, however, representatives can handle six calls per hour. Which queueing model seems appropriate for this situation? Given that slightly more than 35 percent of customers wait over four minutes before a representative answers the call, use this model to estimate how many representatives Mark currently employs.