If the potential energy between two molecules is given by U = - A/r₆+ B/r₁₂, then at equilibrium, the separation between molecules, and the potential energy are:
A. [2B / A]⅙, [-A² / 4B] B. [2B / A]⅙, [-A² / 2B] C. (B / A)⅙, 0 D. (B / 2A)⅙, [-A² / 4B]