If $a_n \to a$ and $b_n \to b$, then $\sum_{k=1}^n \frac{a_kb_{n-k}}{n} \to ab$

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If $a_n \to a$ and $b_n \to b$, then $\sum_{k=1}^n \frac{a_kb_{n-k}}{n} \to ab$.

Is this an application of Cesàro series? If the term $\sum_{k=1}^n {a_kb_{n-k}}$ is a partial sum of some sequence that converges to $ab$. How to do this?