The line \(l\) passes through the points \(A\left( 2,-1,5 \right)\) and \(B\left( -1,-4,2 \right)\).
Find an equation of the line \(l\).
Given that \(P\) is the point \(\left( 4,5,3 \right)\), find the projection vector of \(\overrightarrow{AP}\) onto \(l\). Hence find the position vector of the foot of the perpendicular from the point \(P\) to \(l\).