Let $\overrightarrow{a}=\overrightarrow{i}+\overrightarrow{j}+\hat{k}, \overrightarrow{b}=\hat{i}-\hat{j}+\hat{k} $ and $\overrightarrow{c}=\overrightarrow{i}-\overrightarrow{j}-\overrightarrow{k} $ be three vectors. A vector $\hat{v}$ in the plane of $\overrightarrow{a}$ and $ \overrightarrow{b},$ whose projection on $\overrightarrow{c} $ is $\frac{1}{\sqrt{3}},$ is given by