Alice will flip a coin 8 times and write down the number of heads. Separately, Bob will flip a coin until it lands heads and write down the number of flips. And separately from them, Charlie will draw a number at random from a box with 8 tickets, each labeled with a different integer from 1 through 8.

One of them is selected at random, hides behind a curtain, and gives the game show host the number he or she obtained. The host will give you the number and ask you to guess which person is behind the curtain.

The number is 2. You guess it is Bob. What is the chance you are right?