The arrival of airplanes at an airport can be modeled by a Poisson process with a rate

???? = 5 arrivals per hour.

(i) What is the probability that there will be at least one arrival between 3:30 p.m.

and 5:00 p.m. on a particular day?

(ii) Find the expected value and the variance of the number of airplanes that will arrive between 3:30 p.m. and 5:00 p.m. of that day.