The Draper Clinic has two general practitioners who see patients daily. An average of 6.5 patients arrives at the clinic per hour (Poisson distributed). Each doctor spends an average of 15 minutes (exponentially distributed) with a patient. The patients wait in a waiting area until one of the two doctors is able to see them. However, since patients typically do not feel well when they come to the clinic, the doctors do not believe it is good practice to have a patient wait longer than an average of 20 minutes. Should this clinic add a third doctor, and, if so, will this alleviate the waiting problem?