Derive an expression for energy stored in a stretched wire

If F force applied on wire, wire stretched x .

we know, energy stored in the stretched wire = workdone by force on it.

this is the expression of energy stored in wire , where F is force applied on wire and x is extension of wire.

are there answer choices to this question? this seems like a question where you have options to choose from.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.