(1) An amount received as interest, whether determined at a fixed, variable, or floating rate, on an obligation to pay money to the trustee, including an amount received as consideration for prepaying principal, shall be allocated to income without any provision for amortization of premium.
(2) Except as otherwise provided herein, a trustee shall allocate to principal an amount received from the sale, redemption, or other disposition of an obligation to pay money to the trustee.
(3) The increment in value of a bond or other obligation for the payment of money bearing no stated interest but payable at a future time in excess of the price at which it was issued or purchased, if purchased after issuance, is distributable as income. If the increment in value accrues and becomes payable pursuant to a fixed schedule of appreciation, it may be distributed to the beneficiary who was the income beneficiary at this time of increment from the first principal cash available or, if none is available, when the increment is realized by sale, redemption, or other disposition. When unrealized increment is distributed as income but out of principal, the principal shall be reimbursed for the increment when realized. If, in the reasonable judgment of the trustee, exercised in good faith, the ultimate payment of the bond principal is in doubt, the trustee may withhold the payment of incremental interest to the income beneficiary.