Consider the matrices : $$A=\left[\begin{array}{cc}2 & -5 \\ 3 & m\end{array}\right], B=\left[\begin{array}{l}20 \\ m\end{array}\right]$$ and $$X=\left[\begin{array}{l}x \\ y\end{array}\right]$$. Let the set of all $m$, for which the system of equations $A X=B$ has a negative solution (i.e., $x\lt 0$ and $y\lt 0$), be the interval $(a, b)$. Then $8 \int\limits_a^b |A| \, dm$ is equal to $\underline{\hspace{2cm}}$.