Question: Consider a call center with m = 5 operators that receives, on average, 20 calls per hour. Calls that cannot be immediately served are held in a waiting queue. Each operator costs the employer c = 1/5 units of some currency per minute of conversation. To make profit, each minute of call shall not cost, on average, more than E = 1/3 units of currency. Determine the range of values of the mean service time my for which system is stable and the call-center remains on business.