答案是:Dear Mike; It gives me great pleasure to be invited to attend your graduation ceremony on June 30th in the Shane Hall in our university.I would like to accept your warm invitation but I cannot due to an earlier appointment. Two weeks ago,I made an appointment with one of my former colleagues,Professor Wu Hui, who would come to China to make an academic research.He asked me for help and I have consented.We are going to leave Beijing on June 25th. Therefore,I feel terribly sorry for being unable to attend the event.I wish the graduation ceremony a success: Sincerely yours Wang Lei
