Finding spring constants from an energy graph

[sisi17]

The question gives me a graph of spring 1 and spring 2 (which I will attach to the post) and it asks me what are the springs constants. I have no idea how to find the spring constants. I know that the Potential Elastic equation is (1/2)k(x^2), but I don't know where to start with looking at this graph! Please help!
It's question 1a.

Homework Statement

Homework Equations

E=1/2k(x^2)

The Attempt at a Solution

 

[QuarkCharmer]

Hooke's Law:

$$F = -kx$$

Knowing that, can you find the constant?