(a) Pursuant to 26 U.S.C. 4293,the.S.C. 4251, when the supplies and services are for the exclusive use of the United States. (Secretarial Authorization, June 20, 1947, Internal Revenue Cumulative Bulletin, 1947-1, 205.)

(b) Pursuant to 26 U.S.C. 4483(b), the Secretary of the Treasury has exempted the United States from the federal highway vehicle users tax imposed in 26 U.S.C. 4481. The exemption applies whether the vehicle is owned or leased by the United States. (Secretarial Authorization, Internal Revenue Cumulative Bulletin, 1956-2, 1369.)