A stationary observer is approached by a high-speed train travelling at a speed of $80\,\text{m s}^{-1}$. The horn on the train produces a sound with frequency $250\,\text{Hz}$. The speed of sound is $340\,\text{m s}^{-1}$. What frequency is observed from the horn?
- A$190\,\text{Hz}$
- B$200\,\text{Hz}$
- C$310\,\text{Hz}$
- D$330\,\text{Hz}$