Physics question dont really understand?

A clever engineer designs a “sprong” that obeys the force law Fx =−q(x−xe)3, where xe is the equilibrium position of the end of the sprong and q is the sprong constant. For simplicity, we’ll let xe =0m. Then Fx =−qx3.

A. (qx^4)/4
where q is the sprong constant.

B. (1/2)(m)(v^2)=(1/4)(q)(x^4)
where m is mass of the plastic ball (in kg), v is velocity in m/s, q is the given sprong constant, and x is the given compression of the sprong (in meters).

You can just type in that equation with all the values besides v^2 into Wolfram Alpha and then scroll down to solutions for the answer.