An advisory opinion on any question arising under this part and part 320 of this chapter may be obtained by writing the General Counsel, U.S. Postal Service, 475 L'Enfant Plaza SW., Washington, DC 20260-1100. A numbered series of advisory opinions is available for inspection by the public in the Library of the U.S. Postal Service, and copies of individual opinions may be obtained upon payment of charges for duplicating services.