8. Suppose an individual's utility function is U(X, Y) = XY, and his total budget is $72. The price of Y is always $1, but the price of X increases from $4 to $9. Calculate the substitution effect on X and the income effect on Y. A. SE= -3 X; IE= -18 Y B. SE=+3 X; IE=+18 Y C. SE= -2 X; IE= -36 Y D. SE= +2 X; IE=+12 Y