answer: #Person1# invites #Person2# to lunch, but #Person2# has to do volunteer work this Saturday.
documents: #Person1#: Want to meet for lunch this Saturday?
  #Person2#: Sorry, I can't. I am busy.
  #Person1#: What are you doing?
  #Person2#: I always do volunteer work on the first Saturday of every month.
  #Person1#: What kind of volunteer work?
  #Person2#: I help out at the children's hospital. I help plan activities.
  #Person1#: Oh, yeah?
  #Person2#: Yes, it's exciting. This month we are doing crossword puzzles.