If A=(12)A = \begin{pmatrix} 1 \\ 2 \end{pmatrix}A=(12), what is AATA A^TAAT?
5
(1224)\begin{pmatrix} 1 & 2 \\ 2 & 4 \end{pmatrix}(1224)
(14)\begin{pmatrix} 1 \\ 4 \end{pmatrix}(14)
(14)\begin{pmatrix} 1 & 4 \end{pmatrix}(14)