Solve this problem with the revised simplex method:
Maximize           Z= 5X1 + 3X2 + 2X3
Subject to           4X1+ 5X2 + 2X3 + X4 ≤ 20
                           3X1 + 4X2 - X3 + X4 ≤30
                          X1, X2, X3, X4 ≥ 0
