In allocating receipts and disbursements to or between principal and income, and with respect to any matter within the scope of Articles 2 and 3, a fiduciary:
In exercising the power to adjust under Section 91-17-104(a) or a discretionary power of administration regarding a matter within the scope of this chapter, whether granted by the terms of a trust, a will, or this chapter, a fiduciary shall administer a trust or estate impartially, based on what is fair and reasonable to all of the beneficiaries, except to the extent that the terms of the trust or the will clearly manifest an intention that the fiduciary shall or may favor one or more of the beneficiaries. A determination in accordance with this chapter is presumed to be fair and reasonable to all of the beneficiaries.