Problem 3 (15 pts) A call center has 4 customer service representatives. Each customer's call takes about 10 minutes with a standard deviation of 6 minutes. Customers arrive one every 3 minutes according to an exponential distribution (recall that the standard deviation is equal to the mean for an exponential random variable). Suppose the hourly wage for the staff is 40 dollars per hour per person. Meanwhile, the estimated waiting cost for the customer is 30 dollars per hour per customer. The waiting cost is loss of goodwill due to waiting in line before receiving service. a. On average, how many customers would be waiting in line? b. Shall the call center hire an additional staff member? c. What is the optimal number of staff members for this call center