The simplified form of $\sqrt {294} -\sqrt {150} + 2 \sqrt 6 -3 \sqrt {\large\frac{1}{6}}$ is ________

Question

$\begin{array}{1 1}\frac{2}{7} \sqrt{6} \\ \frac{7}{2} \sqrt{6} \\ \frac{-2}{7} \sqrt{6}\\ \frac{-7}{2} \sqrt{6} \end{array} $