Use Matrices to Represent Systems of Linear Equations

$$\begin{bmatrix} -1 & 3 & 2 \\ -4 & 5 & 7 \\ 1 & -10 & -3 \end{bmatrix} \begin{bmatrix} x \\ y \\ z \end{bmatrix} = \begin{bmatrix} 4 \\ 15 \\ b \end{bmatrix}$$

Find $b$ so that there are an infinite number of solutions to this system of equations.