In a medical office there is only one doctor, who takes an average of 15 minutes to attend to a patient. Patients arrive at the office at an average rate of 3 per hour. Assuming that the arrival time is described by a Poisson distribution and the service time is described by an Exponential distribution, determine the average time that a patient spends waiting to be seen (in hours). a) 1

b) 3

c) 0.75

d) 2.25