Formulate the problem as a transportation linear program. Use the northwest corner rule, Vogel's approximation, and Russell's approximation to find a basic feasible solution.

D.I 9.2-4. The Cost-Less Corp. supplies its four retail outlets from its four plants. The shipping cost per shipment from each plant to each retail outlet is given below. Plants 1,2,3, and 4 make 10, 20,20, and 10 shipments per month, espectively. Retail outlets 1, 2, 3, and 4 need to receive 20, 10, 10 , and 20 shipments per month, respectively