Suppose that the number of drivers who travel between a particular origin and destination during a designated time period has a Poisson distribution with parameter (suggested in the article "Dynamic Ride Sharing: Theory and Practice." J. of Transp. Engr., 1997: 308-312). What is the probability that the number of drivers will

a. Be at most 10?

b. Exceed 20?

c. Be between 10 and 20, inclusive? Be strictly between 10 and 20?

d. Be within 2 standard deviations of the mean value? 85 86 87