(a) In allocating receipts and disbursements to or between principal and income and with respect to any matter within the scope of this chapter, a fiduciary
(1) shall administer a trust or estate in accordance with the governing instrument, even if there is a different provision in this chapter;
(2) may administer a trust or estate by the exercise of a discretionary power of administration regarding a matter within the scope of this chapter given to the fiduciary by the governing instrument, even if the exercise of the power produces a result different from a result required or permitted by this chapter; an inference that the fiduciary has improperly exercised the discretionary power does not arise from the fact that the fiduciary has made an allocation contrary to a provision of this chapter;
(3) shall administer a trust or estate in accordance with this chapter if the governing instrument does not contain a different provision or does not give the fiduciary a discretionary power of administration regarding a matter within the scope of this chapter; and
(4) shall add a receipt or charge a disbursement to principal to the extent that the governing instrument and this chapter do not provide a rule for allocating the receipt or disbursement to or between principal and income.
(b) In exercising a discretionary power of administration regarding a matter within the scope of this chapter, whether granted by the governing instrument or this chapter, including AS 13.38.210 and 13.38.300 - 13.38.435, 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 governing instrument clearly manifests 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.