A box contains 5 red balls, 3 blue balls and 1 black balls. Take two balls out randomly. Let X be number of red balls and Y be the number of black balls. (1) Find the joint distribution of (X; Y ). (2) Find P(X = 1jY = 1).

Fill in the blank 1. a rhombus is a rectangle a) always b) sometimes c) never 2. a square is a quadrilateral a) always b) sometimes c) never 3. a trapezoid is a kite a) always b) sometimes c) never 4. a quadrilateral is a kite a) always b) sometimes c) never 5. a square is a rhombus a) always b) sometimes c) never 6. a parallelogram is a rectangle a) always b) sometimes c) never