answer: Tom is writing to his mother about his part-time job, but #Person1# is surprised that Tom hasn't told his mother because Tom has been working for almost 3 months.
documents: #Person1#: What are you doing, Tom?
  #Person2#: I'm writing to my mother.
  #Person1#: But you wrote to her only yesterday.
  #Person2#: Yes, but I have something new to tell her.
  #Person1#: Something new?
  #Person2#: Yes. I am telling her I've decided to take up a part-time job as a shop assistant.
  #Person1#: What do you mean? You've been working at one nearly three months. Have you been fired by Rogers?
  #Person2#: No. My mother doesn't know I have a part-time job.
  #Person1#: You mean you didn't tell her before?
  #Person2#: No. I didn't want her to worry about my study.
  #Person1#: But why are you telling her now?
  #Person2#: I don't want her to worry about my life here. You see, I told her that I'd just bought a car in my letter.