Convert each of the following linear programs to standard form. a) minimize 2x + y + z subject to x + y 3 y + z 2 b) maximize x1 x2 6x3 2x4 subject to x1 + x2 + x3 + x4 = 3 x1, x2, x3, x4 1 c) minimize w + x y z subject to w + x = 2 y + z = 3 w, x, y, z 0