A unique feature of the exponential distribution is that the standard deviation of its service time is equal to the mean of its service time.

(a) Run the M/M/1 model with an arrival rate of 15 customers per hour and a service rate of 20 customers per hour. What is the average waiting time in the queue (in minutes)?

(b) Now run the M/G/1 model with the same parameters as in part (a). Assume when running that model that the service time is exponentially distributed. What is the average waiting time in the queue (in minutes)? Is your answer the same as for part (a)?