Alithium atom starts from rest at a position x = xo and falls toward zinc atom with an acceleration that depends on their separation as a(x) = 4eϵ/m { 12 (σ^12/σ^13) -6 (σ^6/σ^7) where ϵ, m, and σ are positive constants, and the zinc atom stays fixed at position x = 0, assume that xo > 2^(1/6)σ. a. find an expression for how the velocity of the moving lithium atom depends on x. (it will also depend on ϵ, m, xo and σ) b. what is the distance of closest approach of the the two atoms (in terms of σ and xo)?