4. (10 points) When a fair coin is tossed, 4 points are scored if a head is obtained and 5 points are scored if a tail is obtained. Suppose the coin is tossed three times and let the random variable X be the total score obtained. (a) What are the possible values of X? (b) What is the probability mass function of X? (c) What is the cumulative distribution function of X? (d) What is the expected value and standard deviation of X