8. (12分) Let Y = 5 - 3X. Show that the correlation coefficient ρ{X,Y} =, is equal to -1.0.

4. (12分) Commercial kerosene is stocked in a bulk tank at the beginning of each week.Because of limited supplies, the proportion X of the capacity of the tank available for sale and the proportion Y of the capacity of the tank actually sold during the week are continuous random variables. Their joint distribution is given byFind the covariance of X and Y.