The number of people arriving for treatment at an emergency room can be modeled by a poisson process with a rate parameter of sx per hour (a) what is the probability that exactly four arrivals occur during a partioular hour? (round your answer to three decimal places) 0 134 (b) what is the probability that at least four people arlve during a particular hour? (round your aneswer to three decimal places) (c) how many people de you expect to amlve during a 45-min period? people