Matrix/Standard columns and rows/Exercise

Let $M$ be an $m\times n$- matrix. Show that the matrix product $M{e}_j$ of $M$ with the $j$-th standard vector (regarded as a column vector) is the $j$-th column of $M$. What is $e_{i}M$, where $e_i$ is the $i$-th standard vector (regarded as a row vector)?

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