\left (\begin{array}{cc} 0& 0 \\ 0& 0 \end{array} \right),\ \left (\begin{array}{cc} 0& 0 \\ 0& 0 \end{array} \right),\ \left (\begin{array}{cc} 0& 0 \\ 0& 0 \end{array} \right),\ \left (\begin{array}{cc} 0& 0 \\ 0& 0 \end{array} \right)