A container contains a mixture of two liquids, A and B, in the proponion 7 : 5. If 9 liters of the m.ixmre is replaced by 9 liters of liquid B, then the ratio of the two liquids becomes 7 : 9. How much of liquid A was there in the container initially?

A

21 liters

B

35 liters

C

40 liters

D

19 liters