1. The problem statement, all variables and given/known data Let Y= X1 + X2 and Y2 = X2 + X3 where X1 X2 and X3 are three independent random variables. Find the joint mgf and the correlation coefficient of Y1 and Y2 provided that a) Xi has a Poisson distribution with mean mi i = 1, 2, 3 b) Xi is N(mi, si2) i = 1, 2, 3 3. The attempt at a solution To find the joint mgf, do you have to go through and calculate E(e^(t1y1 + t2y2)) or is there an easier way? Any hints as to how to start.