Let \(a, b \in R\). If the mirror image of the point \(P(a, 6,9)\) with respect to the line \(\frac{x-3}{7}=\frac{y-2}{5…

Let \(a, b \in R\). If the mirror image of the point \(P(a, 6,9)\) with respect to the line \(\frac{x-3}{7}=\frac{y-2}{5}=\frac{z-1}{-9}\) is (20, \(b,-a-9)\), then \(|a+b|\) is equal to:

[JEE Main 2021, 24 Feb (Shift 2)]