The equation of line [latex]l[/latex] is given by [latex]\text{r}=\left( \begin{matrix}2\\1\\0 \\\end{matrix}\right)+\lambda \left( \begin{matrix}1\\-2\\1\\\end{matrix} \right)[/latex]. The coordinates of points [latex]A[/latex] and [latex]B[/latex] are [latex]\left( 1,3,-2 \right)[/latex] and[latex](1,0,-2)[/latex]. Find the length of projection of [latex]\overrightarrow{AB}[/latex] on [latex]l[/latex].