8. Patients arrive for a physical examination according to a Poisson process at the rate 1 per hour. The physical examination requires three stages, each one independently exponentially distributed with a service time of 15 minutes. A patient must go through all the three stages before the next patient is admitted to the treatment facility. a What is the mean and variance of total examination time? o Is this an exponential distribution? 0 Compute the average number of delayed patients, LQ for this system