An aeroplane flies outward at an average speed of $600\,\\text{km h}^{-1}$ and then comes back at $400\,\\text{km h}^{-1}$ along the same distance. What is the average speed for the complete journey?
- A$111\,\\text{m s}^{-1}$
- B$167\,\\text{m s}^{-1}$
- C$480\,\\text{km h}^{-1}$
- D$500\,\\text{km h}^{-1}$