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:
A.R.S. § 14-7417