The Board of Trustees shall designate an actuary who shall: give technical advice to the Board of Trustees on the operation of the funds of the several systems; and perform other related duties that the Board of Trustees requires. On the basis of actuarial assumptions that the Board of Trustees adopts, each year the actuary shall make a valuation of the assets and liabilities of the funds of the several systems and shall recommend the rates of employer contributions to be certified by the Board of Trustees. Each year, on the recommendation of the actuary, the Board of Trustees shall certify to the Secretary of Budget and Management and to the Governor the rates of employer contributions. Each year, on the recommendation of the actuary, the Board of Trustees shall certify to all other participating employers the rates of employer contributions. The normal contribution rate recommended by the actuary and certified by the Board of Trustees for all employers under subparagraph (i) of this paragraph for each fiscal year shall include an amount necessary for the administrative and operational expenses of the Board of Trustees and the State Retirement Agency, excluding the administrative and operational expenses of the Investment Division. For purposes of actuarial valuation, the Board of Trustees may adopt a generally accepted actuarial method for determining the value of the assets held by the several systems. For general ledger accounting and financial reporting, the Board of Trustees shall use generally accepted accounting principles. At least once in each 5–year period, the actuary shall make: actuarial investigations into the compensation, mortality, and service experience of the participants of each of the several systems; and a valuation of the assets and liabilities of the funds of each of the several systems. The Board of Trustees shall: review the results of the investigations and valuations of the actuary; and adopt the actuarial assumptions for each of the several systems as the Board of Trustees considers necessary.