Problem 14 Your probability class has 250 undergraduate stud

Problem 14. Your probability class has 250 undergraduate students and 50 graduate students. The probability of an undergraduate (or graduate) student getting an A is 1/3 (or 1/2, respectively). Let X be the number of students that get an A in your class. (a) Calculate E[X] by first finding the PMF of X. (b) Calculate E[X] by viewing X as a stun of random variables, whom, mean is easily calculated.