Imagine a perfect cube that is placed on a horizontal surface resting on its point (**A**), so that the opposite point (**B** is in the air directly above it. (The long diagonal of this cube (**AB**) would thus be perpendicular to the surface.)

The cube is then cut in half with a horizontal cut - parallel to the surface it is standing on, at the height equal half the length of **AB**, resulting in two equal shapes.

What is the cross-section of such a cut?