Among a sample of diverse coins from an unfamiliar country, each face of any coin portrays one of four things: a judge' s head, an explorer' s head, a building, or a tree
By examining the coins, a collector determines that none of them have heads on both sides and that all coins in the sample with a judge' s head on one side have a tree on the other
All those with an explorer's head on one side have a building on the other.