【正确答案】[范文]
Dear Sam,
   It is lovely to write to you. I haven't seen you since we graduated. I'm told that you are in New York now. What have you been doing these years? Do you keep in touch with other classmates?
   I am now working in Shanghai JiaoTong University as a teaching assistant. My main duty is to support my teacher with her everyday teaching. The job requires great patience. But it is always a nice thing to work in a college, especially with those kind teachers and lovely students.
   I miss you very much. I would be very happy if you come to Shanghai and I'm sure we'll have a good time then. Looking forward to hearing from you.