Jim, Katrina, Larry, and Jim have all been invited to a dinner party. They arrive randomly and each person arrives at a different time.
a. In how many ways can they​ arrive?
b. In how many ways can Jim arrive first and Kim ​last?
c. Find the probability that Jim will arrive first and Kim last.

a.___ (Type an integer)
b.___ (Type an integer.)
c.___ (Type a fraction. Simplify your answer)