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: Mark was swimming with his family. Sentence2: His workplace had called with a few questions for him. Sentence3: He was wading in the water while talking on the phone. Sentence4: Suddenly, the phone slipped from his hand. Sentence5: It fell into the water and broke immediately.
Workplace, Family, Mark