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: I heard my mother cell phone ringing in the kitchen. Sentence2: Since she was in the shower, I took it upon myself to answer it. Sentence3: Someone on the other end of the line demanded to speak with Rick. Sentence4: I told the person no one by that name lived at this address. Sentence5: They apologized for the mistake and hung up, rather rudely on me.
I (myself), Someone, Rick, Mother