Problem $15-31($Algorithmic$)$

Mid$-$West Publishing Company publishes college textbooks. The company operates an $800$ telephone number whereby potential questions about forthcoming texts, request examination copies of texts, and place orders. Currently, two extension lines are use representatives handling the telephone inquiries. Calls occurring when both extension lines are being used receive a busy signal; allowed. Each representative can accommodate an average of $11$ calls per hour. The arrival rate is $22$ calls per hour.