Matrices & Systems · Medium problem

A shipment manifest lists how many of three item types go on each of two trucks, as the rows of $A = \begin{pmatrix}20 & 15 & 10\\12 & 25 & 18\end{pmatrix}$ (columns: item types $1,2,3$). The items weigh $8$, $5$ and $12$ pounds respectively. Truck $2$ has a $500$-pound weight limit. By how many pounds is truck $2$ under its limit?