Suppose there are 20 equally-sized marbles in a bag. Six marbles are blue, seven red, three of them orange, three of them black, and one green. If you choose a red marble, you win nothing. Selecting a blue marble will win you 25 cents. Selecting an orange marble will win you 50 cents, selecting a black marble will cost you a dollar, and if you choose the green one, you win three dollars.