An item is made up of three materials A, B and C. The fraction of material A and B in the item are \(\frac{1}{3}\) and \(\frac{1}{4}\) respectively. The cost per kg of material A and B are Rs. 80 and Rs. 72 respectively. If the total mass of the material is 36 kg and its manufacturing cost is Rs. 2583, then the cost per kg of the material C wll be -