Assume a material with no permanent dipoles, a number density of 1 10^28 m3, and a mass density = 2000 kg m3. Calculate the London dispersion coefficient, Cdisp, if a sphere of this material is adhered to the underside of a smooth surface of the same material against the force of gravity on Earth in a vacuum. The largest radius, R, of sphere that will remain adhered to the surface against the force of gravity is 500 m (micrometers). You may assume that the surfaces are in contact when the separation D is equal to the van der Waals radius of the atoms, or D = 0.2 nm.