Calculate (12)(34)\begin{pmatrix} 1 & 2 \end{pmatrix} \begin{pmatrix} 3 \\ 4 \end{pmatrix}(12)(34).
(38)\begin{pmatrix} 3 & 8 \end{pmatrix}(38)
111111
(3468)\begin{pmatrix} 3 & 4 \\ 6 & 8 \end{pmatrix}(3648)
777