The wavelengths of two sound notes in air are $\large\frac{40}{195}\;$$m$ and $\large\frac{40}{193}\;$$m$. Each note produces 9 beats per second separately with a third note of fixed frequency. The velocity of sound in air in m/s is:

Question

$$\begin {array} {1 1} (a)\;360 & \quad (b)\;320 \\ (c)\;300 & \quad (d)\;340 \end {array}$$