A divorced spouse annuity ends with the earliest of the last day of the month before the month in which the—
(a)
Divorced spouse dies;
(b)
Employee's entitlement to an annuity ends;
(c)
Divorced spouse marries;
(e)
Divorced spouse becomes entitled to a retirement or disability insurance benefit under the Social Security Act based on a primary insurance amount which equals or exceeds the amount of the full divorced spouse annuity before reduction for age.