kindly help me solve this

A \\A IV 9. A fair die is rolled two times. Let X1 and X2 denote the number of points showing on the rst and second rolls, respectively, of a die. Let U =X1+X2 and V :Xl-XQ. (a) Find the mean and variance of V. (b) Find the covariance of U and V. (c) Show that U and V are not independent