(a) The board of trustees shall appoint an executive director.
(b) The executive director shall:
(1) manage and administer the retirement system under the supervision and direction of the board; and
(2) invest the assets of the system.
(c) The board of trustees may delegate to the executive director powers and duties in addition to those stated by Subsection (b).
(d) The executive director annually shall:
(1) prepare an itemized budget showing the amount required to pay the retirement system's expenses for the following fiscal year; and
(2) submit the report to the board for review, amendment, and adoption.