A $50\,\text{kg}$ barrel is pushed up a frictionless plank of length $3.4\,\text{m}$ so that it is loaded onto the rear of a lorry that is $1.6\,\text{m}$ high. What is the least work done?
- A$80\,\text{J}$
- B$170\,\text{J}$
- C$780\,\text{J}$
- D$1700\,\text{J}$