Mid-West Publishing Company publishes college-level textbooks. The company operates an 800 telephone number with which potential buyers can ask questions about future books, request copies of books for review, and place orders. Currently two extensions are used, with two representatives in charge of answering telephone calls. Calls that arrive when both extensions are busy receive a busy signal; waiting is not allowed. Each representative can answer an average of 12 calls per hour. The arrival rate is 20 calls per hour.
What percentage of calls receive a busy signal with the current two-extension telephone system?