A signal which can be green or red with probability $$\frac{4}{5}$$ and $$\frac{1}{5}$$ respectively, is received by station A and then transmitted to station B. The probability of each station receiving the signal correctly is $$\frac{3}{4}$$. If the signal received at station B is green, then the probability that the original signal was green is

A

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

B

$$\frac{6}{7}$$

C

$$\frac{20}{23}$$

D

$$\frac{9}{20}$$