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. To provide faster service, Microdata must first know the current service

rate, so it calculates the service rate under the current system $(1-$ the probability that all

three lines will be busy$).($Carry four decimal places$).$