The random variables X and Y have a joint PDF given by fxy (x, y) = A exp[-(3x + 4y)] u(x)u(y) where u(.) is the unit step function. a) Find the value of A. b) Determine Pr(X > 0.5, Y > 0.25). c) Compute the expected value of XY. r(a) Answer [hint: = x -e-"dx] $8 rang this intergrate 7 a a) A = 12; b) 0.0821; c) 0.0833 by parts