(

a) In lieu of benefits provided by

Section 21620, upon the death of any person, after retirement and while receiving a retirement allowance from this system, there shall be paid to the beneficiary whom he or she shall nominate by written designation duly executed and filed with the board, the sum of six hundred dollars ($600), to be provided from contributions by the employer. (

b) For the purposes of this section, all contributions, liabilities, actuarial interest rates, and other valuation factors shall be determined on the basis of actuarial assumptions and methods that, in the aggregate, are reasonable and that, in combination, offer the actuary’s best estimate of anticipated experience under this system. (

c) The additional employer contributions required under this

section shall be computed as a level percentage of member compensation. The additional contribution rate required at the time this

section is added to a contract shall not be less than the sum of (1) the actuarial normal cost and, (2) the additional contribution required to amortize the increase in accrued liability attributable to benefits elected under this

section over a period of not more than years from the date this

section becomes effective in the contracting agency’s contract. (

d) This

section shall not apply to any contracting agency, except for those contracting agencies that are school employers and those school districts or community college districts, as defined in subdivision (

i) of

Section 20057, until the agency elects to be subject to this

section by amendment to its contract made in the manner prescribed for approval of contracts, except an election among the employees is not required, or, in the case of contracts made after January 1, 1981, by express provision in the contract making the contracting agency subject to this section.