The number of people arriving for treatment at an emergency room can be modeled by a Poisson process with a rate parameter of six per hour. a) What is the probability that exactly three arrivals occur during a particular hour? (Round your answer to three decimal places.)(b) What is the probability that at least three people arrive during a particular hour? (Round your answer to three decimal places.)(c) How many people do you expect to arrive during a 45-min period?