During the morning hours at a catalogue sales department, phone calls come in at an average rate of 40 per hour. Calls that cannot be answered immediately are put on hold. The system can handle eight callers on hold, [f additional calls come in, they receive a busy signal. The three customer service representatives who answer the calls spend an average of three minutes with a customer. Both arrival and service rates are Poisson. What is the probability that a caller will get a busy signal?