Two factories are manufacturing and supplying a single type of good to four warehouses. The factories can produce a1, and a2 units of the good each month, and the warehouses need b1, b2, b3, and b4 units each month, The monthly total of goods available from the two factories exceeds the total of the monthly demands at the 4 warehouses. The cost of supplying one unit of the good from factory "i" to warehouse "j" is Cij. Note that the 2 factories have different factors of production. Their energy and labor costs are very different with one of the factories having much higher electricity rates and employee wages. The costs of production of one unit of the good at factories 1 and 2 and d1 and d2. Set up the problem and constraints; using the algebraic symbols.