Let  $\overline{a}=2\overline{i}-\overline{j}+\overline{k},\overline{b}=\overline{i}+2\overline{j}-\overline{k}$ and $\overline{c}=\overline{i}+\overline{j}-2\overline{k}$ be the three vectors, A vector of the type $\overline{b}+.\lambda \cdot \overline{c}$ for some scalar$\lambda ,$ whose projection on $\overline{a}$ is of magnitude $\sqrt{\frac{2}{3}}$ is