Provide the theme summaries for the following conversation: 

#Person1#: Polly, Ms. Kelly has agreed to come and give a talk about international relations next week. When do you think we can fit her lecture in?
#Person2#: That's Great, Nick. What about Friday afternoon then?
#Person1#: I'm afraid some students are planning to go on a trip. Maybe we can have it on Wednesday afternoon.
#Person2#: No, that's not possible, either. Most students are having group activities for their research projects. Well, I have an idea. I have a class on Tuesday afternoon and probably Ms. Kelly can use my time.
#Person1#: That's possible, but I have to speak to Dr. Lee about that. And you should also talk to the students about the change.
#Person2#: Oh, yes, I'll certainly do that.

Summary: 
Nick asks Polly to arrange Ms. Kelly's lecture. Polly suggests using her class on Tuesday. Nick'll speak to Dr. Lee about that and asks Polly to talk to the students.