A person A can complete a work in 15 days working 8 hours daily. A second person B can complete the same workin 20 days working 7 hours a day. If both A and B work together, working 7 hours a day, then the number of days required to complete that workis

A

8 $$\frac{5}{13}$$

B

9 $$\frac{3}{13}$$

C

9 $$\frac{6}{13}$$

D

10 $$\frac{1}{4}$$