This section may not be construed to limit the authority of the Commissioner to conduct a health benefit plan premium rate review under Title 11, Subtitle 6 of this article. This section applies only to a carrier offering an individual plan and, subject to § 15–1205 of this title, a carrier offering a small group plan. A carrier may determine a premium rate based on: subject to subsection (c) of this section, age; geography based on the following contiguous areas of the State: the Baltimore metropolitan area; the District of Columbia metropolitan area; Western Maryland; and Eastern Maryland and Southern Maryland; subject to subsection (d) of this section, whether the plan covers an individual or a family; and subject to subsection (e) of this section, tobacco use. In this subsection, “age” means an individual’s age as of the date of issuance or renewal of a health benefit plan. For individuals who are 21 years of age or older, a premium rate based on age: may not vary by more than a ratio of 3 to 1 for adults; shall provide for 1–year age bands for individuals at least 21 years old and under the age of 64 years; and shall provide for a single age band for individuals at least 64 years old. For individuals who are under the age of 21 years, a premium rate based on age shall: be actuarially justified and consistent with the uniform age rating curve established in accordance with paragraph (4) of this subsection; provide for a single age band for individuals under the age of 15 years; and provide for 1–year age bands for individuals at least 15 years old and under the age of 20 years. The uniform age rating curve required under paragraph (3)(i) of this subsection may be established by the Commissioner in the individual market, small group market, or both markets. A rating variation for a health benefit plan that provides coverage for a family shall be applied based on the portion of the premium attributable to each family member covered. Subject to subparagraph (ii) of this paragraph, a premium for a health benefit plan that provides coverage for a family shall be determined by summing the premiums for each individual family member. For a health benefit plan that provides family coverage for individuals under the age of 21 years, the sum shall include not more than the premiums for the three oldest individuals under the age of 21 years. A premium rate based on tobacco use may not vary by more than a ratio of 1.5 to 1.