Solution
= Solution
Scalar entries commute, so $B_{jk}A_{ij}=A_{ij}B_{jk}$ is exactly the summed entry formula for <matrix multiplication>. Hence
$$
\boxed{C=AB}.
$$
= Solution
Scalar entries commute, so $B_{jk}A_{ij}=A_{ij}B_{jk}$ is exactly the summed entry formula for <matrix multiplication>. Hence
$$
\boxed{C=AB}.
$$