it's a lot of boring work!! but yes, it's $\displaystyle -728$ the answer.
let me introduce you another example so you can follow the process and apply it in your problem: let $\displaystyle A\in\mathbb M_4$ be matrix such that $\displaystyle A=\left[ \begin{matrix}
1 & 2 & 3 & 4 \\
2 & 2 & 3 & 4 \\
3 & 3 & 3 & 4 \\
4 & 4 & 4 & 4
\end{matrix} \right],$ now let's compute $\displaystyle |A|,$
$\displaystyle \left| A \right|\overset{R_{2}-R_{1}}{\mathop{=}}\,\left| \begin{matrix}
1 & 2 & 3 & 4 \\
1 & 0 & 0 & 0 \\
3 & 3 & 3 & 4 \\
4 & 4 & 4 & 4
\end{matrix} \right|=-\left| \begin{matrix}
2 & 3 & 4 \\
3 & 3 & 4 \\
4 & 4 & 4
\end{matrix} \right|=-\left| \begin{matrix}
2 & 3 & 4 \\
1 & 0 & 0 \\
4 & 4 & 4
\end{matrix} \right|=\left| \begin{matrix}
3 & 4 \\
4 & 4 \\
\end{matrix} \right|=-4.$
does this make sense? the thing is: make zeros and then apply cofactors according to the row or column you created zeros.