Two pipes A and B can fill an empty cistern in 6 hours and 8 hours, respectively. After opening both the pipes simultaneously, pipe B is closed after X hour and A filled the rest of the tank in 4 hours. Then X =

A

$$\frac{8}{12}$$

B

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

C

$$\frac{8}{6}$$

D

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