(a) The members of the board of trustees shall be the trustees of the retirement system and shall have full power to invest and reinvest its assets, subject to all the terms, conditions, limitations, and restrictions imposed by Article 7 of Chapter 20 of this title, the "Public Retirement Systems Investment Authority Law." Subject to like restrictions, the board of trustees shall have the power to hold, transfer, and dispose of any investments in which retirement system assets are invested, including proceeds of investments. The board of trustees is authorized to employ agents, including banks and trust companies, to act as investment advisers and make investments if the board of trustees so authorizes.

(b) For the purpose of meeting disbursements for pensions, annuities, and other payments, the board of trustees may keep available cash on deposit in one or more banks or trust companies organized under the laws of this state or of the United States, provided that the sum on deposit in any one bank or trust company shall not exceed 25 percent of the paid up capital and surplus of each bank or trust company. Each bank or trust company shall give a depository bond in an amount sufficient to cover the deposits or shall place in trust a sufficient amount of federal or state securities to cover the deposits.

(c) Except as otherwise provided in this chapter no trustee or employee of the board of trustees shall have any personal interest in the gains or profits from any investment made by the board of trustees or use the assets of the retirement system in any manner, directly or indirectly, for himself or as an agent, except to make such payments as are authorized by the board of trustees in accordance with this chapter.