A trustee or other fiduciary shall discharge duties with respect to an endowment fund:
(1) solely in the interest of the endowment fund and beneficiaries;
(2) for the exclusive purpose of providing benefits to his beneficiary and paying reasonable expenses of administering the system;
(3) with the care, skill, and caution under the circumstances then prevailing which a prudent person acting in a like capacity and familiar with those matters would use in the conduct of an activity of like character and purpose;
(4) impartially, taking into account any differing interests of beneficiaries;
(5) incurring only those costs that are appropriate and reasonable; and
(6) in accordance with a good faith interpretation of this chapter.