A can complete a work in 15 days. A started the work alone and work for 4 days. B alone complete the remaining work in 18 days. In how many days will A and B together finish the work?

A

$$7\frac{6}{29}$$

B

$$9\frac{9}{29}$$

C

$$11\frac{1}{29}$$

D

$$8\frac{7}{29}$$