The speed of sound in air at standard temperature and pressure is:
(Given the mass of \(1\) mole of air is \(29.0\times10^{-3}~\text{kg}\) and $\mathrm{}$\(\gamma=7/5 \text)\)
1. \(240 ~\text{m/s}\) 
2. \(331.5~\text{m/s}\) 
3. \(384.5~\text{m/s}\) 
4. \(280~\text{m/s}\)