In mixture C, the ratio of milk to water is 5:4, the difference between the quantities of milk and water is ___L, and the cost of the mixture is ₹ 35 per liter. In mixture D, the ratio of milk to water is 4:5, and the difference between the quantities of milk and water is 6 L. When mixtures C and D are mixed together, the cost of the new mixture becomes ₹ 32 per liter. Find the value to be filled in the blank.

(Note: The price of pure milk in both mixtures is the same.)