Problem 6 (10 pts) In a serial system with two servers in sequence, suppose that the interarrival time follows exponential distribution with a mean of 3 minutes. The service time of the first server has a mean of 1 minute with a standard deviation of 2 minutes. The service time of the second server has a mean of 2 minutes with a standard deviation of 1 minute. What is the total cycle time of the serial system