\textbf{194-} A stationary car horn emits a sound wave of $660\ \text{Hz}$. If we approach this stationary car at a speed of $36\ \dfrac{\text{km}}{\text{h}}$, how many hertz do we hear the horn? $\left(\text{speed of sound in air} = 330\ \dfrac{\text{m}}{\text{s}}\right)$
\medskip
(1) $640$ \hfill (2) $660$ \hfill (3) $680$ \hfill (4) $730$
\medskip