Helbe
No
three-wheeled vehicle
Looks to me like it only has two.
An engineer, a physicist and a mathematician are taking a train ride through Scotland when suddenly the engineer says, looking out of the window, "Hey, the Scottish sheep are black!". The physicist corrects him by saying, "No, at least one Scottish sheep is black". Thus the mathematician says, "No, there exists one sheep in Scotland that is black from at least one side".
PS The fourth guy in the compartment, a biologist, just murmurs "Hey guys, that's a goat!".