[tex]\it \left.\begin{aligned} \it \overline{ab}\in M_{34} \Rightarrow \overline{ab}\in\{34,\ 68\}\ \ \ \ \ \ \ \ \ \ \ \ \ \\ \\ \it \overline{cd}\ \vdots\ 43 \Rightarrow \overline{cd}\in M_{43} \Rightarrow \overline{cd}\in\{43,\ 86\}\end{aligned}\right\} \Rightarrow \overline{abcd}\in\{3443,\ 3486,\ 6843,\ 6886\}[/tex]
