answer: Bob invites Nancy to a concert but she has already planned to go to the theatre. Thus, they decide to go to a concert next weekend.
documents: #Person1#: Hello, Nancy. This is Bob. How are you?
  #Person2#: Fine, thank you. A hit too busy though. You know, I'm trying to put everything in order in my new flat.
  #Person1#: Oh, I see. Well, I am wondering if you'd like to go to a concert tomorrow night. I think it will be good. And if I remember correctly, you did say you liked country music.
  #Person2#: Yes. That's fight. It's nice of you to ask, Bob. But I don't think I can. Mother has already asked me to see a friend and then we'll go to the theatre together. In fact she's getting the tickets this evening.
  #Person1#: Oh, well, never mind. What about next weekend? This concert is still on then, I think, if you are free next Saturday.
  #Person2#: Oh, I'd like to very much. But what time exactly?
  #Person1#: It starts at 7:30, I think.
  #Person2#: Oh, good. That'll be fine. The tennis match will be over by 5 o'clock, I'm sure.
  #Person1#: Good, I'll call you again when I get the tickets.
  #Person2#: Sure. Bye.