Binding Energy given a function?

[pinkybear]

Homework Statement

The binding energy of a two-particle system is defined as the energy required to separate the two particles from their state of lowest energy to r=infinity. The potential energy of the two atoms in a diatomic (two-atom) molecule can be written
U(r)=-a/(r^6)+b/(r^12)
where r is the distance between the two atoms and a and b are positive constants.
Determine the binding energy. (in terms of a and b)

Homework Equations

The Attempt at a Solution

I don't even know where to start.. do i take the derivative of U(r) and find the minimum value of r and plug that in which would be the binding energy?

 

[fzero]

Basically, find U_min and U_max. Use the definition given to determine the binding energy.