Example 12.3. A firm making castings uses electric furnace to melt iron with the fol- lou:ing specifications : Minimum Maximum 9127 Carbon 3.20% 3:40% Silicon 2.25% 2.35% Specifications and costs of various raw materials used for this purpose are given be- low: Material Carbon% Silicon% Cost (Rs.) 0.4 0.15 850/tonne 3.80 2.40 900/tonne Remelt from foundary 3.50 2.30 500/tonne If the total charge of iron metal required is 4 tonnes, find the weight in kg of each rau: material that must be used in the optimal mix at minimum cost. Steel scrap Cast iron scrap