The sine of the angle between the two vectors $$a = 3i + j + k$$ and $$b = 2i - 2j + k$$ is

A

$$\sqrt{\frac{74}{99}}$$

B

$$\sqrt{\frac{25}{99}}$$

C

$$\sqrt{\frac{37}{99}}$$

D

$$\sqrt{\frac{5}{51}}$$