According to Hooke's law, the force required to compress or stretch a spring from an equilibrium position is given by F(x)=kx, for some constant k. The value of k (measured in force units per unit length) depends on the physical characteristics of the spring. The constant k is called the spring constant and is always positive.

a. Suppose that it takes a force of 16 N to compress a spring 0.9 m from the equilibrium position. Find the force function, F(x), for the spring described.
b. Setup the integral that will give the work required to stretch the spring 1.3 m from the equilibrium position.
c. Calculate the work done by the force described above.