Motion — practice question

A cyclist travels 300 m uphill in 50 s. She then travels back down the slope in 25 s. What is her average speed for the entire journey?

• A$4.0\,\text{m s}^{-1}$
• B$8.0\,\text{m s}^{-1}$
• C$9.0\,\text{m s}^{-1}$
• D$16\,\text{m s}^{-1}$