answer: #Person1# invites Mary for a walk but Mary needs to return a book, so #Person1# goes with Mary.
documents: #Person1#: Hi Mary. Shall we go out for a walk?
  #Person2#: Well, I'd love to. But you see, I have to return this book to Xiao Ming.
  #Person1#: But you just borrowed it this day last week. Isn't it any good?
  #Person2#: Of course, it is. In fact, I finished it the day before yesterday.
  #Person1#: So shall I go with you?
  #Person2#: Sounds good.