Decide whether a matrix product is defined and give its order
Two matrices \(M\) and \(B\) are given below
\[M = \begin{bmatrix} -3 & 1 & 2 \\ -7 & -9 & -1 \\ -6 & 5 & 9 \\ -1 & -7 & 9 \end{bmatrix}\]
\[B = \begin{bmatrix} 1 & 9 & -8 & -9 \\ -1 & 6 & 6 & -6 \\ -9 & 7 & -2 & -7 \end{bmatrix}\]