$\left(\begin{matrix}5&1&-2&-1\\11&2&3&2\\3&2&3&3\\4&2&3&-2\end{matrix}\right)$

$273$

$\left(\begin{matrix}0&\frac{5}{39}&-\frac{4}{39}&-\frac{1}{39}\\\frac{3}{7}&-\frac{36}{91}&\frac{47}{91}&\frac{15}{91}\\-\frac{2}{7}&\frac{10}{91}&-\frac{8}{91}&\frac{11}{91}\\0&\frac{1}{39}&\frac{7}{39}&-\frac{8}{39}\end{matrix}\right)$

$8$

$\left(\begin{matrix}5&11&3&4\\1&2&2&2\\-2&3&3&3\\-1&2&3&-2\end{matrix}\right)$

$4,4$

$\left(\begin{matrix}1&0&0&0\\0&1&0&0\\0&0&1&0\\0&0&0&1\end{matrix}\right)$