The number of calls that come into a small mail-order company follows a poisson distribution. currently, a single operator services these calls. the manager knows from past experience that an additional operator will be needed if the rate of calls exceeds 20 per hour. the manager observes that 9 calls came into the mail-order company during a randomly selected 15-min a. if the rate of calls is actually 20 per hour, what is the probability that 9 or more calls will come in during a given 15- minute b. if the rate of calls is really 30 per hour, what is the probability that 9 or more calls will come in during a given 15- c. based on the calculations in parts a and b, do you think that the rate of incoming calls is more likely to be 20 or 30 per hour? d. would you advise the manager to hire a second operator? explain.