A source producing sound at a frequency of $1000\ \text{Hz}$ moves directly towards a stationary observer. The observer records the frequency of the sound received as $1500\ \text{Hz}$. The speed of sound in still air is $330\ \text{m s}^{-1}$. What is the speed of the source of sound?
- A$110\ \text{m s}^{-1}$
- B$165\ \text{m s}^{-1}$
- C$220\ \text{m s}^{-1}$
- D$330\ \text{m s}^{-1}$