P, Q and R can complete a piece of work in 10 days, 15 days and 20 days, respectively.
If they work together, in how many days can they finish the same work?

A

$$4\frac{8}{13}$$

B

$$4\frac{3}{7}$$

C

$$4\frac{7}{13}$$

D

$$4\frac{5}{7}$$