For positive constants A and B, the force between two atoms in a molecule is given by the following equation, where r > 0 is the distance between the atoms.

f(r)=-(A/r^2)+(B/r^3)

(a) Find f '(r)

(b) Find the critical point for f(r).

(c) Classify the critical point as a minimum, maximum, or neither.

(d) Find the inflection point for f(r).

I found f'(r) and I got the critical point to be (3b/2a), but am not so sure about that.

Thanks in advance,

Tyler