A refinery distills two crude petroleum, A and B, into three main products: jet fuel, gasoline and lubricants. The two crudes differ in chemical composition and thus, yield different product mixes (the remaining 10 per cent of each barrel is lost to refining): Each barrel of crude A yields 0.4 barrel of jet fuel. 0.3 barrel of gasoline, and 0.2

barrel of lubricants; Each barrel of crude B yields 0.2

barrel of jet fuel, 0.4

barrel of gasoline, and 0.3

barrel of lubricants. The crudes also differ in cost and availability: Up to 5,000 barrels per day of crude $A$ are available at the cost $\$ 25$ per barrel; Up to 3,000 barrels per day of Saudi crude are also available at the lower cost $\$ 18$ per barrel.

Contracts with independent distributors require that the refinery produce 2,000 barrels per day of gasoline, 1,500 barrels per day of jet fuel, and 500 barrels per day of lubricants.