A can complete a work in 5 days and B can complete the same work in 10 days. If A and B work alternately, starting with A, in how many days will they complete the work?

A

$$6\frac{2}{5}$$ days

B

$$6\frac{1}{2}$$ days

C

$$7\frac{2}{5}$$ days

D

$$7\frac{1}{2}$$ days