Solve the homogeneous system and express the solution as a linear combination of basis vectors for the null space: $\begin{bmatrix} 1 & 2 & 0 & 3 \\ 0 & 0 & 1 & 2 \end{bmatrix} \begin{bmatrix} x_1 \\ x_2 \\ x_3 \\ x_4 \end{bmatrix} = \begin{bmatrix} 0 \\ 0 \end{bmatrix}$

What is the dimension of the null space?