Advantage plan that provides qualified prescription drug coverage (an MA–PD plan) and including access to the Medicare Beneficiary Ombudsman under section 1808(c). (b) Enrollment and coverage periods The Secretary shall establish enrollment and coverage periods for individuals who enroll under this section. Such periods shall be established in coordination with the enrollment and coverage periods for plans offered under an Exchange established under title I of the Patient Protection and Affordable Care Act. The Secretary shall establish such periods so that coverage under this section shall first begin on January 1 of the first year beginning at least one year after the date of the enactment of this section and shall include special enrollment periods, in accordance with section 155.420 of title 45 of the Code of Federal Regulations, that are applicable to qualified health plans offered through an Exchange. (c) Buy-In premium (1) Amount of monthly premiums The Secretary shall (beginning for the first year that begins more than 1 year after the date of 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 Subject to subparagraphs (C) and (D), 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