6.72 Suppose that X1 . ... . Xy are independent random variables and that r e R. Ineach part. decide whether the random variables are necessarily independent and explain your answers. X + X; + X, and /Xi+ X + X b) sin(X X2X;) and cos(XyXs) c) sin(X X2Xs) and cos(X3 X4) d) X1 - X2 and Xi + X2 e) min [X1, X2, X7) and max( X3. X4) D E Xx sin(ker) and E X, sin(kr)