mixtures

There are two one-litre cans containing milk and water in the ratios 7: 3 and 8: 2respectively. The contents of the two cans are poured into a two litre can, and the mixture is sold at Rs. 50 per litre, thereby realising a profit of 12.5% on the returns. Find the cost price of a litre of milk if the cost of water is zero.