Consider the system of linear equations involving a matrix representation $AX = B$, where $A = \begin{pmatrix} 1 & 2 & 1 \\ 2 & 4 & 3 \\ 3 & 7 & 3 \end{pmatrix}$ and $B = \begin{pmatrix} 2 \\ 5 \\ 6 \end{pmatrix}$. Which of the following describes the solution set for the vector $X = \begin{pmatrix} x \\ y \\ z \end{pmatrix}$?