Im doing this study and I have this question which I'm not 100% sure on, got me pretty stumped. Anyone think they can help me?

When a bowstring is pulled back in preparation in preparation for shooting an arrow, the string behaves like a spring. Suppose the string is drawn 0.700 m and held with a force of 450 N.
(a) What is the elastic constant of the bow?
(b) How much energy is stored in the string?
(c) Where does the energy stored in the string come from?