Find the basis for the null space of (123012)\begin{pmatrix} 1 & 2 & 3 \\ 0 & 1 & 2 \end{pmatrix}(102132).
{(1,−2,1)}\{(1, -2, 1)\}{(1,−2,1)}
{(1,1,1)}\{(1, 1, 1)\}{(1,1,1)}
{(0,0,0)}\{(0, 0, 0)\}{(0,0,0)}
{(1,2,3)}\{(1, 2, 3)\}{(1,2,3)}