This is my first homework submission. Here you'll find both a .rar file containing the required material, and also what extra work I've done.
Extra 1 - photon mapping
Instead of doing the suggested inter-surface reflections using photon mapping, I decided to try out the much more spectacular-looking caustics effects. I switched to a near-perfectly transmissive glass material, and altered the scene settings to facilitate my objective.
This is the final result, using 500k photons for caustics, and 20k each for the direct and indirect maps. The algorithm has converged to a pretty believable image. See below for some intermediate steps.
Using only 10k photons for caustics, and none for the other maps.