Six stand-up comics, A, B, C, D, E, and F, are to perform on a single evening at a comedy club. The order of performances is determined by random selection. Find the probability that

a. Comic E will perform first

b. Comic C will perform fifth and comic B will perform last

c. the comedians will perform in the following order: D, E, C, A, B, F

d. Comic A or comic B will perform first