a
$| A |=2[3]-1[2]=4$
$\therefore|\operatorname{adj}(\operatorname{adj}(\operatorname{adj} 2 A ))|$
$=|2 A |^{( n -1)^3} \Rightarrow|2 A |^8=16^n$
$\Rightarrow\left(2^3|A|\right)^8=16^n$
$\Rightarrow\left(2^3 \times 2^2\right)^8=16^n$
$=2^{40}=16^n$
$=16^{10}=16^n \Rightarrow n=10$