Subpart C - Income-Related Monthly Adjustments to Medicare Prescription Drug Coverage Premiums Authority:Secs. 702(a)(5), 1860D-13(a) and (c) of the Social Security Act (42 U.S.C. 902(a)(5), 1395w-113(a) and (c)). Source:75 FR 75891, Dec. 7, 2010, unless otherwise noted.