For the purpose of further providing sufficient funds to aid in meeting the cost of benefits provided by §§ 65-151 — 65-168 and to further meet the actuarial requirements of the public service commissioners' retirement fund, there is appropriated to the public service commissioners' retirement fund, in addition to the funds set forth in § 65-161, a sum in an amount to satisfactorily secure the actuarial soundness of the fund annually, commencing with the fiscal year which begins July 1, 1969, such appropriation to be paid out of the unexpended balance standing to the credit of the public service commission in the “motor vehicle account” prescribed by § 65-1518, which account is comprised of the motor carrier inspection, supervision and control fees set forth in said section and of all fines, fees and penalties collected by virtue of the provisions of §§ 65-1501 — 65-1525; and/or out of the unexpended balance standing to the credit of the public service commission in the “public utilities account” prescribed by § 65-431, which account is comprised of the inspection, control and supervision fees and penalties therein required to be paid to the public service commission by public utilities subject to its control and jurisdiction, as prescribed by §§ 65-423 — 65-434. Provided, however, that the funds appropriated by this section shall not exceed four per cent (4%) annually of the balance in the “motor vehicle account” and the “public utilities account” as of the first day of the preceding fiscal year together with a like percentage of all moneys paid into said accounts during such preceding fiscal year. No part of the foregoing appropriation shall be paid from the general funds or revenue of the state of Tennessee but same shall be paid solely out of the aforesaid “motor vehicle account” and/or the aforesaid “public utilities account.”