Suppose that the number of persons using an ATM in any given hour between 9 a.m. and 5 p.m. can be modeled by a Poisson distribution with a mean of 9. In this case, the "unit of measure" is an hour of time during the business day.
What is the probability that more than 10 persons will use the machine between 1 p.m. and 2 p.m.?