4.36 100-Metre Run, again Refer to Exercise 4.14, in which a 100-metre sprint is run by John, Bill, Ed, and Dave. Assume that all the runners are equally qualified, so that any order of finish is equally likely. Use the mn Rule or permutations to answer these questions:

a. How many orders of finish are possible?

b. What is the probability that Dave wins the sprint?

c. What is the probability that Dave wins and John places second?

d. What is the probability that Ed finishes last?