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