An unstretched spring that follows Hooke’s Law has a length of $10\,\text{cm}$. A load with weight $20\,\text{N}$ is attached to the spring. After this, the spring’s length becomes $36\,\text{cm}$. Calculate the spring constant $k$ for the spring.
- A$0.56\,\text{N cm}^{-1}$
- B$0.77\,\text{N cm}^{-1}$
- C$1.3\,\text{N cm}^{-1}$
- D$1.8\,\text{N cm}^{-1}$