If
$$\begin{aligned}\mathbf{b}_{1}=&\left[\begin{array}{r}2 \\-1 \\4\end{array}\right], \quad \mathbf{b}_{2}=\left[\begin{array}{r}5 \\7 \\-6\end{array}\right] \\\mathbf{b}_{3}=\left[\begin{array}{l}0 \\
0 \\0\end{array}\right], & \mathbf{b}_{4}=\left[\begin{array}{l}1 \\2 \\3\end{array}\right]\end{aligned}$$
write the matrix $B=\left[\mathbf{b}_{1}, \mathbf{b}_{2}, \mathbf{b}_{3}, \mathbf{b}_{4}\right],$ and determine
the row vectors of $B$