Line is $\frac{x+1}{2}=\frac{y-3}{-2}=\frac{z}{-1}=\lambda:$ Let point $R$ is
$(2 \lambda-1,-2 \lambda+3,-\lambda)$
Direction ratio of $PQ \equiv(2 \lambda-2,-2 \lambda+1,3-\lambda)$
$PO$ is $\perp^{ r }$ to line
$ \Rightarrow 2(2 \lambda-2)-2(-2 \lambda+1)-1(3-\lambda)=0 $
$ 4 \lambda-4+4 \lambda-2-3+\lambda=0$
$ 9 \lambda=9 \Rightarrow \lambda=1$
$\Rightarrow $ Point R is $(1, 1, -1) $
$\begin{matrix}\frac{a+1}{2}=1\\ a=1\end{matrix} \begin{vmatrix}\frac{b+2}{2}=1\\ b=0\end{vmatrix}\begin{matrix}\frac{c-3}{2}=-1\\ c=1\end{matrix}$
$\Rightarrow a+b+c=2$
