The mean increase in the U.S. population is about four people per minute. Find the probability that the increase in the U.S. population in any given minute is 

(a) Exactly six people, 

(b) More than eight people, and 

(c) At most four people.

Find the indicated probabilities using the geometric distribution, the Poisson distribution, or the binomial distribution. Then determine whether the events are unusual. If convenient, use a table or technology to find the probabilities.