A sum of money becomes $$\frac{8}{7}$$ of itself in 2 years at a certain rate of simple interest.
The rate per annum is:

A

$$6 \frac{3}{7}\%$$

B

$$8 \frac{1}{7}\%$$

C

$$7 \frac{1}{7}\%$$

D

$$7 \frac{3}{7}\%$$