Decide whether a matrix product is defined and give its order
Consider the matrices \(Q\) and \(B\) shown below
\[Q = \begin{bmatrix} -3 & -1 \\ -7 & -3 \\ -9 & 0 \end{bmatrix}\]
\[B = \begin{bmatrix} 7 & 9 \\ -5 & -4 \\ -6 & 0 \\ 0 & 1 \end{bmatrix}\]