question from The Great Calculus Caper 2009,

If the volume of the cone of light was decreasing at a rate of 16 cubic feet per second, I figured the radius of the beam would increase at a rate of 7 ft/sec and the height decrease at 6 ft/sec. I asked myself, "how far (to the nearest foot) from the scoundrel would I have to be for all of these facts to come together and illuminate him in an 8 foot radius of light?