空穴

空 = 工 + 穴 : Mnemonic symbol: an air conditioner

空 = 工 + 穴 : In front of the engine, Karl Koala found some very special cave paintings. Using steel beams he constructs a protective cover. He also installs air conditioning to make the best environment possible to preserve the cave paintings.

穴 = 八 + 宀 : Xu Xian presents his newest piece of art: Cave paintings painted on a gigantic eight-ball. Somehow he managed to set it up inside the elevators entrance. For his great artistic achievement, he gained a honorary doctor, and proudly wears his hard earned graduation cap.