| $x$ | 10 | 12 | 14 | 15 | 17 | 18 |
| $f$ | 5 | 8 | 7 | 10 | 6 | 4 |
\textbf{140.} The mathematics scores of 40 students of a class are given in the following table. What is the weighted mean of the scores?
\begin{center}
\begin{tabular}{|c|c|c|c|c|c|c|}
\hline
$x$ & 10 & 12 & 14 & 15 & 17 & 18 \\
\hline
$f$ & 5 & 8 & 7 & 10 & 6 & 4 \\
\hline
\end{tabular}
\end{center}
(1) $14.2$ \hfill (2) $14.25$ \hfill (3) $14.4$ \hfill (4) $14.75$
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