Q: 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: Mark was bad at math. Sentence2: He tried studying, but to no avail. Sentence3: Then his mom hired a private tutor. Sentence4: She helped Mark study after school each day. Sentence5: With her help, Mark improved his grades dramatically!
A:
Private tutor, Mark's mom, Mark