Let B1,B2,B_1,B_2,B1,B2, and B3B_3B3 be standard Brownian Motions. Find Cov(B1(1)+B2(1),B2(2)+B3(2))\text{Cov}(B_1(1) + B_2(1), B_2(2) + B_3(2))Cov(B1(1)+B2(1),B2(2)+B3(2)).