Walking at $$\frac{3}{5}$$ of his usual speed, a man covers a certain distance in one hour and 40 minutes more than the time he takes to cover the distance at his usual speed. The time taken by him to cover the same distance at his usual speed is:

A

$$\frac{7}{2}$$ hours

B

$$\frac{3}{2}$$ hours

C

$$\frac{5}{2}$$ hours

D

$$\frac{5}{3}$$ hours