You have volunteered to be tested for psychic powers. There are 8 cards, 2 of which have a square on them, 2 of which have a triangle on them, 2 of which have a circle on them, and 2 of which have a star on them. The tester shuffles the cards, then looks at each card in turn, without letting you see it, and tries to send the picture psychically to you. You guess a picture randomly each time. Let X be the number of times you guess correctly