shall be applied as if the reference to July 1, 2021 under such paragraph were a reference to the later of the 6th full calendar quarter after the day on which the drug was first marketed or July 1, 2021. (C) Exemption for shortages The Secretary may reduce or waive the rebate under paragraph (1)(B) with respect to a part B rebatable drug that appears on the drug shortage list in effect under section 506(e) of the Federal Food, Drug, and Cosmetic Act or in the case of other exigent circumstances, as determined by the Secretary. (5) Application to beneficiary coinsurance In the case of a part B rebatable drug for which a rebate is payable under this subsection— (A) in computing the amount of any coinsurance applicable under this title to an individual with respect to such drug, the computation of such coinsurance shall be based on the inflation-adjusted payment amount determined under paragraph (3)(C) for such part B rebatable drug