The logistics manager has the problem of shipping materials in warehouses to customer locations as illustrated in Fig.
Warehouses are in Phoenix, Austin and Gainesville, the gray nodes in the figure.
The supplies available are indicated in the brackets adjacent to the nodes with a positive number indicating a supply of the material. Customers are in Chicago, Los Angeles, Dallas, Atlanta and New York. The negative numbers adjacent to these nodes are the demands. Possible air shipping links are the directed arcs between the nodes. The numbers adjacent to the arcs are unit shipping costs.