Assume the probability density function of two Random Variable X1 and X2 is: Let Z1 = X1 + X2 and Z2 = X1 / (X1 + X2) a) What is the joint pdf for (Z1, Z2) b) What is the marginal pdf of Z2? What is the name of the distribution? c) Are Z1 and Z2 independent?fX1,X2(x1,x2)={exp{(x1+x2)},0,forx10,x20elsewhere.