It is the intent of this chapter to establish an equal shares concept of retirement plan funding which shall require that all costs of benefits, from whatever source resulting, attributable to or based on service on and after April 1, 1935, payable to or on account of persons who are members under this plan shall be borne equally on a share and share alike basis by the members of the plan as a group on one hand, and the city on the other; provided, however, that on or after the effective date of this chapter, the actuary retained by the board for purpose of determining the member's contribution rates under Section 2.124.930 of this chapter shall assume, in addition to all other actuarial assumptions: (1) that all persons who enter the employ of the city on or after the effective date of this chapter and who would have been eligible for membership in this plan under former (1976) Charter Section 302 and ordinances enacted thereunder, are members of this plan if they would have remained in the employ of the city; and (2) that no person who was a member of this plan on the effective date of this chapter has elected or will elect to become a member of the Section 399 retirement plan. The term "costs" as used herein and in succeeding sections shall not include the usual, normal, and reasonable administrative costs of the retirement system, which shall be borne by the city. (Prior code § 34.05.541)