You will be given a definition of a task first, then some input of the task.
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: Jack had been struggling with his math homework. Sentence2: He thought that if he tried hard enough that his grade would improve. Sentence3: Jack got his report card and his grade was a D. Sentence4: Jack and his mother discussed his grade and Jack agreed to get a tutor. Sentence5: The tutor worked with Jack all quarter and his grade improved to a B.
Output:
His mother, Jack, A tutor