Problem 2.. A factory has received an order for three different types of casting weighing respectively 18, 45 and 27 tonnes. 10% of the raw materials used are wasted in manufacturing and are sold as scrap for 20% of the cost price of raw materials. The cost of raw materials is Rs. 250 per tonne, the wages for three types of castings are respectively Rs. 4,000, Rs. 10,500 and Rs. 5,500. The cost of the moulds for the three different types of castings are respectively Rs. 400, Rs. 500 and Rs. 300. If the factory overhead charges are 40% of the wages in each case, find the cost of production per tonne of each type of casting