b
(b) Minor of $-4$ = $\left| {\begin{array}{*{20}{c}}{ - 2}&3\\8&9\end{array}\,} \right| = - 42$,
$9$ = $\left| {\begin{array}{*{20}{c}}{ - 1}&{ - 2}\\{ - 4}&{ - 5}\end{array}} \right| = - 3$
and cofactor of $ -4$ =${( - 1)^{2 + 1}}( - 42) = 42$,
cofactor of $9$= ${( - 1)^{3 + 3}}( - 3) = - 3$ .