You take a 20-question multiple-choice exam. Each question has 4 possible answers (only one of which is correct). You ne

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You take a 20-question multiple-choice exam. Each question has 4
possible answers (only one of which is correct). You need at least
60% to pass the course.
a) Suppose you are sure you answered the first 6 questions
correctly. Otherwise, you answer randomly. What is the probability
that you will pass?
b) If you eliminate a choice that seems impossible to you, how
much will your chance increase?
c) Give the distribution function of the total correct answers
for the strategy in and make its graph. Give the median number of
your correct answers.