The city may budget and provide by ordinance for payment into the fund of the retirement system an amount sufficient:

(1) To provide, on an actuarial reserve basis, the amortized level premium cost of the retirement benefits which, under the provision of the retirement system, are to be provided by the city to its officers or employees who attain the retirement age or retire in accordance with the terms of the retirement plan.

(2) To meet the actuarially computed costs of retirement benefits measured on the basis of services rendered or to be rendered by an officer or employee before or after the date on which such officer or employee becomes a member of the retirement plan. [Formerly 238.540]