An Olymipic archer is able to hit the bull's-eye 80% of the time. Assume each shot is independent of the others. If she shoots 6 arrows, what's the probability of each result described below.
a. Her first bull's-eye comes on the third arrow.
b. She misses the bull's-eye at least once.
c. Her first bull's-eye comes on the fourth or fifth arrow.
d. She gets exactly 4 bull's-eyes
e. She gets at least 4 bull's-eyes
f. She gets at most 4 bull's0-eyes