A distribution company produces its product at two different factories (50 units at F1 and 40 units at F2) to meet a demand for its product at its two warehouses (30 units at W1, and 60 units at W2), sometimes via a distribution center (DC). From F1 it costs $900/unit to ship to W1, $400/unit to ship to DC, and $200/unit (up to 10 units) to ship to F2. From F2 the units can only be shipped to DC at a cost of $300/unit. From DC a maximum of 80 units can be shipped to W2 at a cost of$100/unit. In addition, units can be shipped from W1 to W2 at $300/unit and from W2 to W1 at $200/unit. How should the goods be shipped to minimize transportation cost?