Find the indicated probabilities using the geometric distribution, the Poisson distribution, or the binomial distribution. Then determine if the events are unusual. If convenient, use the appropriate probability table or technology to find the probabilities. The mean number of heart transplants performed per day in a country is about six. Find the probability that the number of heart transplants performed on any given day is (a) exactly seven, (b) at least eight, and (c) no more than three