Raju, Sunil and Vishal can separately finish a work in 20, 30 and 40 days, respectively.
In how many days Raju can finish the work, if he is assisted by Sunil and Vishal on alternate days, starting with Sunil?

A

$$12\frac{3}{5}$$

B

$$12\frac{1}{20}$$

C

$$11\frac{1}{20}$$

D

$$11\frac{3}{5}$$