- Problem 6.4 from Revelle et al. You will formulate this problem mathematically, but you will not solve the problem. Transportation problem with production costs (not the usual transportation problem).Two factories are manufacturing and supplying a single type of good to four warehouses in different parts of the country. The factories can produce a1 and a2 units of the good each month, and the warehouses need b1,b2b3 and b4 units each month. The monthly total goods available from the two factories exceeds the total of the monthly demands at the four warehouses. The costs of supplying one unit of the good from factory i to warehouse j is cij. The two factories have different factors of projection. Their energy and labor costs are very different, with one of the factories having much higher electricity rates and employee wages. The cost of production of one unit of good at factories 1 and 2 are d1 and d2. Structure the objective function and the constraints for this problem in expanded form (without the summation sign)