A product made in two factories, P and Q, is transported to two destinations, R and S. The per unit cost of transportation (in Rupees) from factories to destinations are as per the following matrix.

Factory P produces 7 units and factory Q produces 9 units of the product. Each destination requires 8 units. If the north-west corner method provides the total transportation cost as X (in Rupees) and the optimized (the minimum) total transportation cost is Y (in Rupees), in (X – Y), in rupees, is