((a)) The annuity that a person is entitled to elect under section 1431 or 1432 of this title shall, in conformance with actuarial tables selected by the Board of Actuaries under , be the amount specified by the elector at the time of the election, but not more than 50 percent nor less than 12½ percent of his retired or retainer pay, in no case less than $25. He may make the annuity payable—

((1)) to, or on behalf of, the surviving spouse, ending when the spouse dies or, if the spouse remarries before age 60, when the spouse remarries;

((2)) in equal shares to, or on behalf of, the surviving children eligible for the annuity at the time each payment is due, ending when there is no surviving eligible child; or

((3)) to, or on behalf of, the surviving spouse, and after the death of that spouse or the remarriage of that spouse before age 60, in equal shares to, or on behalf of, the surviving eligible children, ending when there is no surviving eligible child.

((b)) A person may elect to provide both the annuity provided in clause (1) of subsection (a) and that provided in clause (2) of subsection (a), but the combined amount of the annuities may not be more than 50 percent nor less than 12½ percent of his retired or retainer pay but in no case less than $25.

((c)) An election of any annuity under clause (1) or (2) of subsection (a), or any combination of annuities under subsection (b), shall provide that no deduction may be made from the elector’s retired or retainer pay after the last day of the month in which there is no beneficiary who would be eligible for the annuity if the elector died. For the purposes of the preceding sentence, a child (other than a child who is incapable of supporting himself because of a mental defect or physical incapacity existing before his eighteenth birthday) who is at least eighteen, but under twenty-three years of age, and who is not pursuing a course of study or training defined in , shall be considered an eligible beneficiary unless the Secretary concerned approves an application submitted by the member under . An election of an annuity under clause (3) of subsection (a) shall provide that no deduction may be made from the elector’s retired or retainer pay after the last day of the month in which there is no eligible spouse because of death or divorce.

((d)) Under regulations prescribed under , a person may, before or after the first day for which retired or retainer pay is granted, provided for allocating, during the period of the surviving spouse’s eligibility, a part of the annuity under subsection (a)(3) for payment to those of his surviving children who are not children of that spouse.

((e)) Whenever there is an increase in retired and retainer pay under , each annuity that is payable under this subchapter on the day before the effective date of that increase to a spouse or child of a member who died on or before , shall be increased by the same percentage as the percentage of that increase, effective on the effective date of that increase.