Consider two random variables X and Y whose joint probability density function is given by c ifx + y 2 1, x ) = 0 otherwise, where c is a constant that needs to be determined. (a) What is the value of c? (b) What is the joint cumulative distribution function Fx.r(x, y)? Hint: Consider five cases (you may want to plot these cases in the x-y plane): (1) x + y > 1, 0 1; (4) 0 1; (5) x > landy > 1