A sledge with a mass of $50\,\text{kg}$ is resting on snow. It is dragged horizontally for $10\,\text{m}$ while opposing a friction force of $200\,\text{N}$, and then it is pulled horizontally over ice for another $10\,\text{m}$. The ice exerts no friction on the sledge. Next, it is raised vertically by $1\,\text{m}$ and, finally, it is taken back to its starting point at constant speed. In which part of the journey is the greatest amount of work done on the sledge?
- Abeing carried back $20\,\text{m}$ at constant speed
- Bbeing lifted up $1\,\text{m}$
- Cbeing pulled $10\,\text{m}$ across ice
- Dbeing pulled $10\,\text{m}$ across snow