A spring of natural length $15.0\,\text{cm}$ extends by $4.0\,\text{cm}$ when a mass weighing $6.0\,\text{N}$ is hung from it. The spring does not go beyond the limit of proportionality. What is the full length of the spring when the suspended mass has a weight of $3.0\,\text{N}$?
- A$2.0\,\text{cm}$
- B$7.5\,\text{cm}$
- C$9.5\,\text{cm}$
- D$17.0\,\text{cm}$