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Q: A multiple-choice examination consists of 90 questions, each having possible choices a, b, c, d, and e. Approximate the probability that a student will get at least 21 answers correct if she randomly guesses at each answer. (Note that, if she randomly guesses at each answer, then the probability that she gets any one answer correct is 0.2.) Use the normal approximation to the binomial with a correction for continuity.