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

The vector (s) which is/are coplanar with vectors $${\widehat i + \widehat j + 2\widehat k}$$ and $${\widehat i + 2\widehat j + \widehat k,}$$ and perpendicular to the vector $${\widehat i + \widehat j + \widehat k}$$ is/are