$\left. \begin{matrix}    CA=50,\widehat{A}=\widehat{C}  \\  \widehat{B}=25,\widehat{B}=\widehat{D}  \\ \end{matrix} \right\}\Rightarrow \widehat{M}=\widehat{A}+\widehat{D}=50+25=75$