Given the task definition and input, reply with output. In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.

Sentence1: Rachel was good at running. Sentence2: She challenged her friend Bob to a race. Sentence3: Bob agreed to the race. Sentence4: Rachel won the race. Sentence5: Bob congratulated Rachel on her win.
Bob, Rachel