Hi Maddy. We made a drawing of the problem using Geogebra. You can find it here. If you rotate the figure you can notice how the spheres touch the cube in $2$ points each, and the "plaster" around them is all connected, so it made no sense to "remove the outer edge" as the original problem asked (that would have resulted in removing ALL the plaster, so no sculpture in the end :/). The way the problem was reworded afterwards may not produce a nice sculpture, but at least has a unique answer.