If the Postal Service determines that any document or other matter it provides to the Postal Regulatory Commission under a subpoena issued under subsection (f), or otherwise at the request of the Commission in connection with any proceeding or other purpose under this title, contains information which is described in
section 410(c) of this title, or exempt from public disclosure under
section 552(b) of title 5, the Postal Service shall, at the time of providing such matter to the Commission, notify the Commission, in writing, of its determination (and the reasons therefor).