Let $A=\left[\begin{array}{cc}-0\mathrm{.}6& 1\mathrm{.}3\\ 2\mathrm{.}4& -1\mathrm{.}9\end{array}\right]$

$($a$)$ Find the determinant of $A.($Include at least two decimal places in your answer.$)$

$($b$)$ Using your result from part $($a$),$ find $A^{-1}.($Include at least three decimal places in your answers.$)$