Two pipes A and B can fill an empty tank in 6 hours and 8 hours respectively. After opening both of them for t hours the pipe B is closed and the pipe A filled the rest of the tank in 4 hours. Then t =

A

$$\frac{8}{7}$$

B

$$\frac{8}{3}$$

C

$$\frac{4}{3}$$

D

$$\frac{2}{3}$$