If A=(12)A = \begin{pmatrix} 1 \\ 2 \end{pmatrix}A=(12), what is ATAA^T AATA?
555
(1004)\begin{pmatrix} 1 & 0 \\ 0 & 4 \end{pmatrix}(1004)
(1224)\begin{pmatrix} 1 & 2 \\ 2 & 4 \end{pmatrix}(1224)
333