Microdata Software, Inc., uses a telephone ordering system for its computer software productions. Callers place orders with Microdata by using the company$$s $800$ telephone number. Assume that calls to this telephone number arrive at a rate of $15$ calls per hour. The time required to process a telephone order varies considerably from order to order. However. Each Microdata sales representative can be expected to handle $6$ calls per hour. Currently, the Microdata $800$ telephone number has three internal lines, each operated by a separate sales representative. Calls received on the $800$ number are automatically transferred to an open line if available. Whenever all three lines are busy, callers receive a busy signal. In the past, Microdata management assumed that callers receiving a busy signal would call back later. However, recent research showed that a substantial number of callers who are denied access do not call back later. These lost calls represent lost revenues for the firm, so Microdata$$s management requested an analysis of the telephone ordering system. If management$$s goal is to provide sufficient capacity to handle $90\%$ of the callers, how many telephone lines and sales representatives should Microdata use? $($Carry four decimal places$).$