Vector Algebra

If $\overrightarrow a ,\overrightarrow b ,\overrightarrow c$ are three non-zero vectors and $\widehat n$ is a unit vector perpendicular to $\overrightarrow c$ such that $\overrightarrow a = \alpha \overrightarrow b - \widehat n,(\alpha \ne 0)$ and $\overrightarrow b \,.\overrightarrow c = 12$, then $\left| {\overrightarrow c \times (\overrightarrow a \times \overrightarrow b )} \right|$ is equal to :