A company has three coal mines, 1, 2, and 3, and ships coal to four customers: A, B, C, and D. The number of tons of coal required by A,B,C, and D are 80,70,60, and 40 , respectively. The production cost is $50 per ton of coal at coal mine 1. Coal mine 1's production capacity is 120 tons. The ash content in each ton of coal produced at coal mine 1 is 0.08 tons. The sulfur content in each ton of coal produced at coal mine 1 is 0.05 tons. The production cost is $55 per ton of coal at coal mine 2. Coal mine 2's production capacity is 100 tons. The ash content in each ton of coal produced at coal mine 2 is 0.06 tons. The sulfur content in each ton of coal produced at coal mine 2 is 0.04 tons. The production cost is $62 per ton of coal at coal mine 3. Coal mine 3's production capacity is 140 tons. The ash content in each ton of coal produced at coal mine 3 is 0.04 tons. The sulfur content in each ton of coal produced at coal mine 3 is 0.03 tons. Table 1 is the shipping cost (in dollars) per ton of coal from a coal mine to a customer. For each customer, the total amount of coal received must contain at most 5% ash and at most 4% sulfur. Please formulate a mathematical model that minimizes the cost of meeting customer demands. Please use GAMS to find the optimal solution. Table 1. Shipping Cost per Ton of Coal