Q2. A fair die is rolled. Let the random variable X to be the sum of the face value of each roll. Each roll is independent. (a) Mean and variance if the die is rolled once. (b) What is the probability that the r.v X is greater than 9 if the die is rolled twice? (c) What is the mean and variance of the r.v X if a dice is rolled 40 times? (d) What is the probability that the r.v X is greater than 200 but less than 220 if a dice is rolled 40 times?