the enactment of this section), during September of the preceding year, determine a monthly premium for individuals enrolled under this section. Such monthly premium shall be equal to 1/12 of the annual premium computed under paragraph (2)(B), which shall apply with respect to coverage provided under this section for any month in such year. (2) Annual premium (A) Combined National, per capita average for parts A, B, and D benefits The Secretary shall estimate the average, annual per capita amount for benefits and administrative expenses that will be payable under parts A, B, and D in the year for all individuals enrolled under this section. (B) Annual premium The annual premium under this subsection for months in a year is equal to the average, annual per capita amount estimated under subparagraph (A) for the year. (C) Adjustments The Secretary shall adjust the annual premium under this subsection as necessary— (i) to ensure that expenditures under this title for any year are not increased by reason of this section