Mary, Bob, and Alice are playing a noisy game in the park where you are trying to read. The two girls are as boisterous as the boy ruining your hopes of a quiet afternoon. You look up with a sigh and the woman sitting next to you catches your eye.
"I do hope my children aren't disturbing you." she says.
"It's alright," you reply politely, "It must be hard to manage three kids at that age."
"Oh only two are mine!" she laughs, "Alice and ______"

What is the probability that
    *   she ends with "Bob"         =   ___%
    *   she ends with "Mary"        =   ___%

Think about it!