A can do a piece of work in 12 days and B can do it in 30 days. They work on alternate days; starting with A. In how many days will the work be completed?

A

$$16\frac{4}{5}$$

B

$$17\frac{1}{7}$$

C

$$16\frac{4}{7}$$

D

$$17\frac{2}{5}$$