4.97. Find a subset of u1, u2, u3, u4 that gives a basis for W = span(ui) of R5, where
(a) u1 = (1, 1, 1, 2, 3), u2 = (1, 2, -1, -2, 1), u3 = (3, 5, -1, -2, 5), u4 = (1, 2, 1, -1, 4)
(b) u1 = (1, -2, 1, 3, -1), u2 = (-2, 4, -2, -6, 2), u3 = (1, -3, 1, 2, 1), u4 = (3, -7, 3, 8, -1)
(c) u1 = (1, 0, 1, 0, 1), u2 = (1, 1, 2, 1, 0), u3 = (2, 1, 3, 1, 1), u4 = (1, 2, 1, 1, 1)
(d) u1 = (1, 0, 1, 1, 1), u2 = (2, 1, 2, 0, 1), u3 = (1, 1, 2, 3, 4), u4 = (4, 2, 5, 4, 6)