A layer of dust is formed h units thick by the fall of meteors to the earth from all directions. Find the rate of change of the density due to this effect in terms of the density of the earth, D, the density of the dust, d, the radius of the earth, R, and the layer thickness, h. The moment of inertia of a solid sphere is 2/5 MR and of a thin hollow sphere is 2/3 mR^3.