Suppose that the arrival of calls that arrive at an office are described by a Poisson process. The office is open for 8 hours a day, and the probability of receiving no calls in a given day is 10-7 (a) Compute the value of the parameter u so that D, the number of calls received in a day, has a Pois(u) distribution. (b) Describe the distribution of the random variable B, which describes the number of calls that arrive in the first hour of business. (c) Describe the distribution of the random variable L, which describes the number of calls that arrive in the last hour of business.