My father visited my family last year. After his six month stay, I renewed his B-2 visa usin his original I-94 card. Before the approval of his B-2 extension application, he went back to China. About one month ago, I received his B-2 extension approval. I would like to mail the I-94 along with his boarding passes to show that he left US. Please advise where I should send these documents, regional INS, Airport Immigration Office, or other place. Thanks.