Let us draw a card at random from an ordinary deck of cards. Define the random variable X in the following way: X=4 if an ace is drawn, X=3 if a king is drawn, X=2 if a queen is drawn, X=1 if a jack is drawn, and X=0 for any other card. Give the probability mass function, f(x) of X. Solution (a) The probability mass function is: 1/13(4) + 1/13(3) + 1/13(2) + 1/13(1) + 9/13(0).