Which of the following is the correct transformation to convert the second-order recurrence $a_n = c_1 a_{n-1} + c_2 a_{n-2}$ into a first-order system $\mathbf{v}_n = M \mathbf{v}_{n-1}$, where $\mathbf{v}_n = \begin{pmatrix} a_n \\ a_{n-1} \end{pmatrix}$?