Thanks a lot, But

my lawyer give P.O box
P.O. Box 87140
Lincoln, NE 68501-7140

the PO box on my RFE letter is
P.O. Box 82521
Lincoln, NE 68501-2521

I don't know which one I should use. Is there any advantage of using PO box than using street address (or disadvantage)?

Also, do different people have different P.O. boxes to mail their I140 RFE (NSC)?

Thanks a million to clarify these questions for me.