Sec. 25. (a) Except as provided in subsection (b), and unless otherwise provided by the governing instrument, the unitrust amount shall be considered to have been paid from net income. The net income of the trust shall be determined as if the trust were not a unitrust.
(b) To the extent that:
(1) net income is insufficient to pay the unitrust amount, the unitrust amount shall be considered to have been paid from net realized short term capital gains;
(2) net income and net realized short term capital gains are insufficient to pay the unitrust amount, the unitrust amount shall be considered to have been paid from net realized long term capital gains; and
(3) net income and net realized short term and net long term capital gains are insufficient to pay the unitrust amount, the unitrust amount shall be considered to have been paid from the principal of the trust.