The number of calls coming into a child abuse hotline during the 5 p.m. to 9 a.m. period on weekdays had a Poisson distribution with an average of 1.67 calls per hour. Call lengths had Exponential distribution with average of 5.4 minutes. It is considered important that a very' high percentage of calls get through to the operator right away (as opposed to having to wait), [f only one person is assigned to answer the phones, what is the probability that a call will have to wait because the operator is busy?