Let v1, , vk be vectors, and suppose that a point mass of m1, , mk is located at the tip of each vector. the center of mass for this set of point masses is equal to v = m1v1 + + mkvk m where m = m1 + + mk. determine how to divide a total mass of 13 kg among the vectors u1 = (−1, 3), u2 = (3, −2), and u3 = (5, 2) so that the center of mass is (31/13, 10/13).