Pedestrian traffic is being monitored at the southeast corner of the intersection of 8th Avenue and 14th Street to determine whether a crossing signal is needed there. The average number of pedestrians arriving at the corner is four per minute. Assume all the Poisson conditions are met. Use the Poisson probability function to calculate the probability that
a. Exactly one pedestrian will arrive in a given minute.
b. No pedestrians will arrive in a given minute.
c. At least two pedestrians will arrive in the next minute.
d. No more than one pedestrian will arrive in the next 30 seconds.