Transporting Coal. The Calcio Coal Company produces coal at four mines and ships it to four power plants (P1-P4). The cost per ton of producing coal and the production capacity (in tons) for wach mine are known. The number of tons of each coal demanded by each customer is also known. The cost (in dollars) of shipping a ton of coal from a mine to each plant is available as well. The following table provides the data: P1 P2 P3 P4 Capacity Cost Mine 1 9 15 8 10 125 50 Mine 2 7 15 14 12 100 57 Mine 3 5 5 11 12 150 55 Mine 4 3 6 8 11 120 61 Demands 110 115 135 130 a. Calcio wishes to minimize the cost of transporting coal from its mines to its plants. A.)What is the optimal transportation plan for Calcio Coal Co.? B.) What is the marginal value of additional production capacity at each one of the four mines?