For a binomial probability distribution, it is unusual for the number of successes to be less than 2.5 or greater than +

For a binomial probability distribution, it is unusual for the number of successes to be less than μ − 2.5σ or greater than μ + 2.5σ.
(a) For a binomial experiment with 10 trials for which the probability of success on a single trial is 0.2, is it unusual to have more than five successes? Explain.
(b) If you were simply guessing on a multiple-choice exam consisting of 10 questions with five possible responses for each question, would you be likely to get more than half of the questions correct? Explain.