A person is standing beside a straight railway line. A train travels towards the person and sound is produced by its whistle. As the train comes nearer, the person hears a sound with frequency $1690\,\text{Hz}$. When the train has passed and is moving away, the person hears a sound with frequency $1500\,\text{Hz}$. The speed of sound in air is $340\,\text{m s}^{-1}$. Determine the speed of the train.
- A$20\,\text{m s}^{-1}$
- B$38\,\text{m s}^{-1}$
- C$41\,\text{m s}^{-1}$
- D$43\,\text{m s}^{-1}$