answer: Tony will go to the US for the summer vacation while Joan will have to stay in the school to serve American students.
documents: #Person1#: Do you have anything planned for the summer vacation Tony?
  #Person2#: Well, I'll go to the US with the exchange students. What about you Joan?
  #Person1#: I'd wanted to go to Singapore to stay with my aunt when the vacation begins. But the headmaster told me I should stay in the school to help the students from the US to choose which family to stay with. And act as their guide when they go sightseeing in Tokyo.
  #Person2#: What about your trip to Singapore, then?
  #Person1#: Well, I've invited my aunt to come here. Have you decided when to leave?
  #Person2#: Yes on July fourth, and will stay there until the end of the month.
  #Person1#: Have you found someone to look after your house?
  #Person2#: Yes, my cousin will come from Beijing to learn Japanese, he'll live in my house during my absence.