Problem 4. During the early morning hours, customers arrive at a branch post office at an average of 4 minutes per customer (Poisson), while clerks can handle transactions in an average time (exponential) of 6 minutes each. Please find the following: (Please keep four decimal places). a. The average time of customers waiting for service if two clerks are used (provide your answer in minutes). b. If three clerks are used, how much will customer waiting time be reduced (in minutes)? C. If the hourly wage for a clerk is $20 and the estimated average cost of customer waiting time is $50 per hour, what is the optimal number of clerks such that the total cost is at the lowest possible?