Let the angle $\theta ,0 < \theta < \frac{\pi }{2}$ between two-unit vectors $\hat a$ and $\hat b$ be ${\sin ^{ - 1}}\left( {\frac{{\sqrt {65} }}{9}} \right)$. If the vector $\vec c = 3\hat a + 6\hat b + 9(\hat a \times \hat b)$, then the value of $9(\vec c \cdot \hat a) - 3(\vec c \cdot \hat b)$ is