The graph illustrates how the extension of a sample of a type of rubber changes as varying loads $F$ are applied and then slowly withdrawn. What is the best estimate of the strain energy in the rubber when a load of $80\,\text{N}$ is applied?
- A$0.40\,\text{J}$
- B$0.64\,\text{J}$
- C$0.88\,\text{J}$
- D$1.3\,\text{J}$