Mathematics - Vector Question with Solution | TestHub

Let $\overrightarrow{c}$ be a vector perpendicular to the vectors $\overrightarrow{a}=\hat{i}+\hat{j}-\hat{k}$ and $\overrightarrow{b}=\hat{i}+2\hat{j}+\hat{k}$. If $\overrightarrow{c}·(\hat{i}+\hat{j}+3\hat{k})=8$, then the value of $\overrightarrow{c}·(\overrightarrow{a}\times \overrightarrow{b})$ is equal to