\textbf{194-} A sound source moves at constant speed. The wavelength in front of the source is $5_0$ m and the wavelength behind the source is $6_0$ m. If the source stops, the wavelength of the emitted sound will be how many $0_0$ m?
(1) $0_0\,66$ \hfill (2) $0_0\,60$ \hfill (3) $0_0\,55$ \hfill (4) $0_0\,50$