"The Patient Protection and Affordable Care Act (Act) requires the Department of Health and Human Services to determine how the actuarial value of qualified health plans (QHPs) and other nongrandfathered coverage in the individual and small group markets will be calculated.... The Bulletin emphasizes that the calculation is based on the provision of [essential health benefits] to a standard population, not the population covered by the plan, since the [actuarial value] is expected to be used by consumers in comparing the relative value of plans with different cost sharing designs."