a
$\left|\mathrm{P}^{-1} \mathrm{AP}-2 \mathrm{I}\right|$ $ =\left|\mathrm{P}^{-1} \mathrm{AP}-2 \mathrm{P}^{-1} \mathrm{P}\right|$
$ =\left|\mathrm{P}^{-1}(\mathrm{~A}-2 \mathrm{I}) \mathrm{P}\right|$
$ =\left|\mathrm{P}^{-1}\right||\mathrm{A}-2 \mathrm{I}||\mathrm{P}| $
$=|\mathrm{A}-2 \mathrm{I}|$
$=\left|\begin{array}{llc}0 & 1 & 2 \\ 6 & 0 & 11 \\ 3 & 3 & 0\end{array}\right|=69$
So, Prime factor of $69$ is $3 \& 23$
So, sum $=26$