Calculate the estimated cost of production of by-products X and Y at the point of separation from the main product. By-product X By-product Y Selling price per unit Rs. 12 Rs. 24 Cost per unit after separation from the main product Rs. 3 Rs. 5 Units produced 500 200 Selling expenses amount to 25% of total works cost, that is, including both pre-separation and post- separation work cost. Selling prices are arrived at by adding 20% of total cost, that is the sum of works cost and selling expenses.