to the Administrator each estimate requested pursuant to item (aa) relating to a calendar year by not later than February 28 of that calendar year. . 8. Cellulosic biofuel credits Section 211(o) of the Clean Air Act ( 42 U.S.C. 7545(o) ) is amended, in paragraph (4) (as redesignated by section 5(b)(1)(B))— (1) in subparagraph (C)— (A) by striking A credit and inserting the following: (i) In general Subject to clause (ii), a credit