3d Geometry

If the lines \({{x - 1} \over 1} = {{y - 2} \over 2} = {{z + 3} \over 1}\) and \({{x - a} \over 2} = {{y + 2} \over 3} = {{z - 3} \over 1}\) intersect at the point P, then the distance of the point P from the plane \(z = a\) is :