A publisher finds that the mean number of grammatical errors per page of a book is six. Find the probability that the number of grammatical errors found on any given page is

(a) exactly four,

(b) at most four,

(c) more than four.

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.