Giovanni makes random guesses on his Statistics multiple-choice test, which has five choices for each question. We want to know how many questions Giovanni answers until e gets one correct.

a. On average, how many questions must Giovanni answer before he gets the first one correct?

b. What is the probability that Giovanni's first correct answer occurs on the fourth question?

c. What is the probability that Giovanni's first correct answer occurs within the first 6 questions?

d. What is the probability that Giovanni's first correct answer occurs within the first ten questions?