If $\vec{a} = 2\hat{\text{i}} + 3\hat{\text{j}} - \hat{\text{k}}$, $\vec{b} = -\hat{\text{i}} + 2\hat{\text{j}} - 4\hat{\text{k}}$ and $\vec{c} = \hat{\text{i}} + \hat{\text{j}} - 2\hat{\text{k}}$, then $(\vec{a} \times \vec{b}) \cdot (\vec{a} \times \vec{c}) =$