A monkey randomly hits a keyboard with 26 letters, one per
second.
(a) How long, in average, will it take for the monkey to type
the letter Z for the first time?
I believe that each letter is random and independent, meaning
that the probability of the monkey typing any letter is (1/26).
Therefore, the expected value is equal to the sum from 1 to 26
times (1/26), yielding 13.5 seconds. I am unsure how to move
forward with parts...