An infinite plane (z=0) has the free charge density σ.  On top is a dielectric of thickness d with dielectric constant εr.  Beneath the plane is a dielectric (also thickness d) having dielectric constant 2εr.  Find D,  E, P, and the bound charges everywhere.

I tried using a Gaussian box to find D, but that didn't work.  Please help, will rate as a lifesaver for any suggestions.