1.Poisson distribution.

You want to determine the probabilities that a specific number of patients will arrive at the emergency room in a one-minute interval during the afternoon. There could be zero patients arrived, one patient, two patients, and so on. If the mean of arrivals per minute is 4,

a) Find the probability of exactly three arrivals in the next minute.

b) Find the probability of two or fewer patient arrivals per minute at the emergency.