(a) The board of trustees shall compensate all persons whom it employs and shall pay all expenses necessary to operate the retirement system at rates and in amounts approved by the board. Those rates and amounts may not exceed those paid for the same or similar service for the state.
(b) Except as provided by Subsection (c), the board of trustees shall pay compensation and expenses required by Subsection (a) from the expense account.

(c) The board of trustees shall make payments from the law enforcement and custodial officer supplemental retirement fund for services rendered by the actuary for that fund and approved by the board.
(d) The board of trustees may compensate employees of the retirement system, whether subject to or exempt from the overtime provisions of the Fair Labor Standards Act of 1938 (29 U.S.C. § 201 et seq.), at the rate equal to the employees’ regular rate of pay for work performed on a legal holiday or for other compensatory time accrued, when taking compensatory time off would be disruptive to the system’s normal business functions.
(e) The retirement system is exempt from Subchapter K, Chapter 659, and Chapter 660, to the extent the board of trustees determines an exemption is necessary for the performance of fiduciary duties.