i. 1. The van der Waals pair potential for two atoms or small groups of diameter o is given by U(r)=-C/* for r. Show that the interaction between a molecule and a surface is given by U()=-1Cp/(6r"), where p is the density of atoms within the surface, and the interaction between two parallel chain molecules (polymers) composed of monomer units of these groups is U ( )=-32C/80r*) per unit length. Assume that ro in all cases