A light string has a length of \(1.4 ~\text m \) when subjected to a tension of \(5 ~\text N\) and a length of \(1.56 ~\text m\) when the tension is increased to \(7 ~\text N.\) Assuming the string obeys Hooke’s law, what is its natural length?
1. \(1\) m
2. \(10\) m
3. \(17\) m
4. \(20\) m