(a) Where the secretary is required by the regulations in this part to give notice to any person, this shall be done by delivering or mailing such notice to the person at the address for service that the said person has furnished to the Commission, or if no such address has been furnished, at the dwelling house or usual place of abode or usual place of business of such person.

(b) Where the secretary is required by the regulations in this part to give notice to a Government, this shall be done by delivering or mailing such notice to the Secretary of State for External Affairs of Canada or to the Secretary of State of the United States of America, as the case may be.

(c) Service of any document pursuant to § 401.22 shall be by delivering a copy thereof to the person named therein, or by leaving the same at the dwelling house or usual place of abode or usual place of business of such person. The person serving the notice or request shall furnish an affidavit to the secretary stating the time and place of such service.