Snake oil. Seriously. Melt snow in northern climes? Think about it. IF there were enough sunlight to melt snow, why didn't the sunlight just, you know, melt the snow? Are they THAT much more efficient at absorbing the sun's energy? I don't think so.
Cost to buy, cost to install, cost to maintain, ... the economics just don't make sense.
Had the author simplified the formula for "Vanswer" rather than plugging in values for h & c, he would have gotten:
Vanswer = (Pi/6) * h^3
From which is it easy to see that the answer in this particular case is 36 * Pi but it also makes clear that the answer does not depend on R.