4. Three different material handling units are available for moving items of material. The costs of these lifts are $3000, $2500, and $3300, respec- tively. These units must make six moves. Data on the operating cost, W. and the operating time, hi, are given in the accompanying table. Deter- mine which type of equipment should be used. Move Wij huj W21 h2 W3i 0.5 50 60 70 0.3 1 2 3 4 5 6 0.7 0.8 0.9 0.8 0.7 0.4 0.5 0.1 0.2 40 70 M 100 80 50 30 60 40 M 80 0.2 0.3 0.2 50 0.1 100 40 M