A company is considering opening warehouses in four cities: New York, Los Angeles, Chicago, and Atlanta.

Each warehouse can ship 100 units per week. The weekly fixed cost of keeping each warehouse open is

$400 for New York, $500 for Los Angeles, $300 for Chicago, and $150 for Atlanta. Region 1 of the country requires 80 units per week, region 2 requires 70 units per week, and region 3 requires 40 units per week. The costs (including production and shipping costs) of sending 1 unit from a warehouse to a region are shown in the file P06_50.xlsx. The company wants to meet weekly demands at minimum cost, subject to the preceding information and the following restrictions:

■ If the New York warehouse is opened, then the Los Angeles warehouse must be opened.

■ At most two warehouses can be opened.

■ Either the Atlanta or the Los Angeles warehouse must be opened.