 $$\widetilde{a}=\left[ \begin{array}{cc} 0.0 &\ 0.0\\ 0&\ 0.0 \end{array} \right], \widetilde{b}=\left[ \begin{array}{cc} 0.0 &\ 0.0\\ 0&\ 0.0 \end{array} \right],\widetilde{c}=\left[ \begin{array}{cc} 0.0&\ 0 \\ 0.0&\ 0.0 \end{array} \right].$$  