\textbf{191-} A guitar string closed on both ends has a mass of 4 grams, a cross-sectional diameter of 1 millimeter, and a length of 40 centimeters. If the string is stretched with a force of 30 Newtons, what is the fundamental frequency? $(\pi = 3)$
\begin{center}
(1) 125 \hspace{1cm} (2) 250 \hspace{1cm} (3) 375 \hspace{1cm} (4) 500
\end{center}