4. In a single-server queuing situation, the system is simulated for 100 hours. The results of the simulation show that the server was busy only during the following time intervals: (0, 10), (15, 20), (25,30), (35,60), (70, 80), and (90,95). The length of the transient period is estimated to be 10 hours.

(a) Define the observation start point needed to implement the regenerative method.

(b) Compute the 95% confidence interval for the average utilization of the server based on the regenerative method.

(c) Apply the subinterval method to the same problem using a sample size n = 5. Compute the corresponding 95% confidence interval, and compare it with the one obtained from the regenerative method.