Qusetion: Patients arrive for a physical examination aecording 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 three stages before the next patient is .admitted to the treatment facility. Compute the average number of delayed patients, La, for this system. (Hint: The variance of the sum of independent random variables is the sum of the variance.)