; cost-Sharing Section 1833(a) of the Social Security Act ( 42 U.S.C. 1395l(a) ) is amended— (1) in paragraph (1)— (A) in subparagraph (S), by striking with respect to and inserting subject to subparagraph (DD), with respect to ; (B) by striking and (CC) and inserting (CC) ; and (C) by inserting before the semicolon at the end the following: , and (DD) with respect to a part B rebatable drug (as defined in paragraph (2) of section 1834(x)) for which a rebate is payable under such section, the amounts paid shall be the difference between (i) the payment amount under paragraph (3)(A)(ii)(I) of such section for such drug, and (ii) 20 percent of the inflation-adjusted payment amount under paragraph (3)(A)(ii)(II) of such section for such drug ; and (2) by adding at the end of the flush left matter following paragraph (9), the following: For purposes of applying paragraph (1)(DD) and section 1834(x)(5), the Secretary shall make such estimates and use such data as the Secretary determines appropriate. . (c) Conforming amendment to part B ASP calculation Section 1847A(c)(3) of the Social Security Act (42 U.S.C. 1395w–3a(c)(3)) is amended by inserting or section 1834(x) after section 1927 .