Two vessels a and b contain milk and water respectively. The vol of milk in A and vol of water are in the ratio 4:5. Now, x lit of milk from A is poured into B and then y lit of the sol from B is poured into A. If as a result, the conc. of milk in A and that of water in B both dropped from 100% to 66 2/3%, find x:y.

1) 7:4
2) 5:3
3) 3:2
4) cannot be determoned