Upgrade subject to access all content

If $b$ is a real number, the linear system:

$$\begin{align*} 2x+3y&=1\\\ 4x+7y&=b\end{align*}$$

Is inconsistent for all $b$

Has infinitely many solutions, regardless of $b$

Has a unique solution, only when $b=\pm 1$

Has a unique solution for each real number $b$