If A=(20)A = \begin{pmatrix} 2 & 0 \end{pmatrix}A=(20), what is ATAA^T AATA?
(4000)\begin{pmatrix} 4 & 0 \\ 0 & 0 \end{pmatrix}(4000)
(4)\begin{pmatrix} 4 \end{pmatrix}(4)
(2)\begin{pmatrix} 2 \end{pmatrix}(2)
(0004)\begin{pmatrix} 0 & 0 \\ 0 & 4 \end{pmatrix}(0004)