The Potential Energy for the Interaction Between the Two Atoms

The potential energy for the interaction between the two atoms in a diatomic molecule is U = A/x¹² - B/x⁶, where A and B are constants and x is the interatomic distance. The magnitude of the force of one atom exerts on the other is:

A) 12A/|x|¹³ - 6B/|x|⁷
B) -13A/|x|¹³ + 7B/|x|⁷
C) -11A/|x|¹¹ + 5B/|x|⁵
D) 72A/|x|¹² - 72B/|x|⁶
E) A/|x|¹³ - B/|x|⁷