Pipes A and B can fill a tank in 8 hours and 12 hours, respectively. C is an outlet pipe. When all the three are opened together, the tank is filled in $$13\frac{1}{3}$$ hours. C alone can empty the full tank in:

A

$$6\frac{1}{2}$$ hours

B

$$7\frac{1}{2}$$ hours

C

$$8$$ hours

D

$$6$$ hours