A can do as much work in 4 days as B can do in 5, and B can do as much work in 6 days as C in 7. In what time will C do a piece of work which A can do in a week ?

A

$$\frac{5}{24}$$

B

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

C

$$\frac{8}{15}$$

D

$$\frac{6}{19}$$