Matrices & Systems · Medium problem

Let $A = \begin{pmatrix}1 & 3 & -3 \\ -2 & 1 & 3\end{pmatrix}$ and $B = \begin{pmatrix}4 & 3 \\ 2 & 3 \\ -1 & -1\end{pmatrix}$. Find the entry in row $1$, column $1$ of $AB$.