A spring has a natural length of 10 in. An 800-lb force stretches the spring to 14 in.

A. Find the force constant.

work= force times displacement- though that applies here I do not know.

B. How much work is done in stretching the spring from 10 in to 12 in?

I have no idea.

C How far beyond its natural length will a 1600-lb force stretch the spring?

No idea.

All I understand is the boundaries are [10,14].

Thanks!