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A queueing system has customers arriving at the rate of 31 per hour, exponentially distributed. Servers can process customers at the rate of 2 per hour, exponentially distributed. There are multiple servers. a) What is the minimum number of servers required? b) Suppose that servers are paid a wage of $10/hour. Further suppose that customers are annoyed at having to wait for service. In fact, we value customers' waiting time at the rate of $20 per hour. In other words, we treat each hour that each customer waits as a cost of $20. What is the total hourly cost (wages plus annoyance) if we use the minimum number of servers? c) What is the number of servers to use that minimizes the total hourly cost