If a trustee determines that an allocation between principal and income required by section 14-7418, 14-7419, 14-7420, 14-7421 or 14-7424 is insubstantial, the trustee may allocate the entire amount to principal unless one of the circumstances described in section 14-7403, subsection C applies to the allocation. This power may be exercised by a cotrustee in the circumstances described in section 14-7403, subsection D and may be released for the reasons and in the manner described in section 14-7403, subsection E. An allocation is presumed to be insubstantial if either:
1. The amount of the allocation would increase or decrease net income in an accounting period, as determined before the allocation, by less than ten per cent.
2. The value of the asset producing the receipt for which the allocation would be made is less than ten per cent of the total value of the trust's assets at the beginning of the accounting period.