Answer
$-3$
Work Step by Step
We know that for a matrix
\[
\left[\begin{array}{rrr}
a & b & c \\
d &e & f \\
g &h & i \\
\end{array} \right]
\]
the determinant, $D=a(ei-fh)-b(di-fg)+c(dh-eg).$
Hence here $D=5(7-6)-1(42-42)+4(12-14)=5(1)-1(0)+4(-2)=5-0-8=-3$
