Two solutions A and B of acid and water contain acid and water in the ratio 7 : 9 and 5 : 3, respectively. A and B are mixed in the ratio $$x$$ : y. If the ratio of acid and water in the resulting solution is 9 : 7, then $$x$$ : y is:

A

4 : 5

B

2 : 3

C

1 : 2

D

3 : 4