4. Suppose matrix \( A=\left[\begin{array}{cccc}1 & -2 & 3 & 0 \\ -3 & 1 & 0 & -1 \\ 2 & 0 & 2 & 4 \\ 4 & 3 & -1 & 9\end{array}\right] \), red reduce it to echelon form and find its rank.