A multiple-choice exam consists of 16 questions, each with five alternatives. A student needs to answer at least 12 of the questions correctly in order to pass the exam. (a) What is the probability that George passes the exam if he guesses at random on each question? What is George's expected number of correct answers? What is the variance of the number of his correct answers? (b) What is the probability that Ann passes the exam if she knows the first two answers and guesses at random on the rest:? What is Ann's