An athlete covers $300\,\text{m}$ up a hill in $100\,\text{s}$. She then goes back down the same hill in $50\,\text{s}$. What is her average speed for the entire run?
- A$2.0\,\text{m s}^{-1}$
- B$4.0\,\text{m s}^{-1}$
- C$8.0\,\text{m s}^{-1}$
- D$9.0\,\text{m s}^{-1}$