Vectors - Projection Lengths

The coordinates of points \(A\) and \(B\) are \(\left( 3,1,-2 \right)\) and \(\left( 7,4,-5 \right)\). Find the exact length of projection of \(\overrightarrow{AB}\) on \({{l}_{1}}:\mathbf{r}=\left( \begin{matrix} -12  \\  -22  \\  11  \end{matrix} \right)+\lambda \left( \begin{matrix} 4  \\ 4  \\-7  \\ \end{matrix} \right);\lambda \in \mathbb{R}\).