Find a set of vectors spanning the solution space of Ax=0where $\displaystyle

\[

A =

\left[ {\begin{array}{cccc}

1 & 0 & 1 & 0 \\

1 & 2 & 3 & 1 \\

2 & 1 & 3 & 1 \\

1 & 1 & 2 & 1 \\

\end{array} } \right]

\]

$

So I rref and it's row equivalent to the identity matrix. How do I interpret the result?