If X1, X2, X3, and X4 are (pairwise) uncorrelated random variables, each having mean 0 and variance 1, compute the correlations of: (a) X1 + X2 and X2 + X3 (b) X1 + X2 and X3 + X4

2. If X1,X2,X3, and X4 are (pairwise) uncorrelated random variables, each having mean 0 and variance 1, compute the correlations of: (a) X1 + X2 and X2 + X3 (b) X1 + X2 and X3 + X4