Chapter 8.4, Problem 28MS

Crime story (ExH). Suppose 20 witnesses saw someone commit a crime, and each supplied a piece of information. One witness said the perpetrator was wearing a certain type of shoe. Another said the perpetrator was taller than six feet. A third said the perpetrator had dark hair, and so on. Each piece of inform ation distinguished the perpetrator only from half the people on Earth. The different pieces were independent in the sense that any combination of them was possible. If there are roughly 6.6 billion people on Earth, approximately how many would fit all 20 of the pieces of information?