Section 228.1 - Introduction(a)What does this part include? This part includes the computation of a widow(er)'s, disabled widow(er)'s, remarried widow(er)'s, surviving divorced spouse's, parent's, and child's insurance annuity under the Railroad Retirement Act. This part describes the two annuity components or tiers which are included in these annuities. The tier I annuity component, which may be payable in all of the above annuities, is described in subpart B of this part. Subpart C of this part describes the tier II annuity component which is only applicable to the widow(er)'s, disabled widow(er)'s, parent's, and child's annuity.(b)Other relevant parts.(1) Part 225, Primary Insurance Amount Determinations, describes the various types of primary insurance amounts which form the basis of the computation of the tier I annuity component described in this part.(2) Part 216, Eligibility for an Annuity, describes the eligibility requirements for receipt of the annuity computations described in this part.