P does some work in 4 hours. The same is done by P and Q together in 3 hours, Q and R together in 2 hours. Working together, how many hours will they take to do the same work?

A

$$\frac{6}{7}$$ hours

B

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

C

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

D

$$\frac{5}{7}$$ hours