The RREF of a system is: $\begin{bmatrix} 1 & 0 & 4 & 2 & | & 5 \\ 0 & 1 & 3 & -1 & | & 2 \\ 0 & 0 & 0 & 0 & | & 0 \end{bmatrix}$

Identify the free variables (parameters that can take any value).