Suppose that X and Y represent the amount of money in the wallets of players A and B, respectively. Let X and Y be jointly uniformly distributed on the unit square [0, 1] x [0, 1]. A and B each places his wallet on the table. Whoever has the smallest amount of money in his wallet, wins all the money in the other wallet. Let WA be the amount of money that player A will win. Show that E(WA) = 0. (For a history of this problem, see Exercise 28 in the Review Problems of Chapter 8.)