A source of sound waves is travelling at a steady speed straight towards a stationary observer. The sound waves move at $340\,\text{m s}^{-1}$ and have a frequency of $480\,\text{Hz}$. The observer detects sound waves with frequency $650\,\text{Hz}$. What is the speed of the source?
- A$89\,\text{m s}^{-1}$
- B$120\,\text{m s}^{-1}$
- C$250\,\text{m s}^{-1}$
- D$340\,\text{m s}^{-1}$