F nine executives in a business firm, four are married, three have never married, and two are divorced. Three of the executives are to be selected for promotion. Let Y1 denote the number of married executives and Y2 denote the number of never-married executives among the three selected for promotion. Assume that the three are randomly selected from the nine available. We determined that the joint probability distribution of Y1, the number of married executives, and Y2, the number of never-married executives, is given by p(y1, y2) = 4 y1 3 y2 2 3 − y1 − y2 9 3 where y1 and y2 are integers, 0 ≤ y1 ≤ 3, 0 ≤ y2 ≤ 3, and 1 ≤ y1 + y2 ≤ 3. (a) Find the marginal probability distribution of Y1, the number of married executives among the three selected for promotion. (Enter your probabilities as fractions.)