An engineer, a mathematician, and a biologist are sitting outside of a building drinking coffee ... They see two people enter the building, and a minute later, the same two people come back out with a third person along side them. The biologist exclaims, ""they multiplied!"" The engineer comments, ""No, it must have just be a calculation error."" The mathematician finally said, ""Look, it doesn't matter how that third person got there, but what we do know is that if someone enters the building iβ¦