Which of these is the RREF of (2412)\begin{pmatrix} 2 & 4 \\ 1 & 2 \end{pmatrix}(2142)?
(1200)\begin{pmatrix} 1 & 2 \\ 0 & 0 \end{pmatrix}(1020)
(1001)\begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}(1001)
(0100)\begin{pmatrix} 0 & 1 \\ 0 & 0 \end{pmatrix}(0010)
(2400)\begin{pmatrix} 2 & 4 \\ 0 & 0 \end{pmatrix}(2040)