The value of $$\frac{3}{15} + \frac{3}{14} - \frac{19}{21} + \frac{31}{35} - \frac{23}{30}$$ is:

A

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

B

$$\frac{1}{3}$$

C

$$\frac{12}{35}$$

D

$$\frac{8}{21}$$