This problem concerns a cube with sides of length 10cm. 

The base of the cube is labelled ABCD anticlockwise (looking from above). The top of the cube is labelled EFGH, also anticlockwise looking from above, so that E is above A, F is above B, G is above C and H is above D.

The cube is split into three pyramids which are congruent to the pyramid with vertices ABCDE.

State the volume of each of these pyramids, and calculate the exact surface area of each pyramid, without using a calculator.

Bonus question: what geometrical result about pyramids do these three pyramids illustrate?