(a) The taxable income of a resident estate or resident trust means its federal taxable income modified by the addition or subtraction, as the case may be, of its share of the fiduciary adjustment determined under § 1634 of this title.
(b) In the case of an electing small business trust as defined in § 1361(e) of the Internal Revenue Code [26 U.S.C. § 1361(e)] there shall be added to the amount calculated pursuant to subsection (a) of this section, to the extent not otherwise included in such amount, the taxable income of the portion of the trust consisting of S corporation stock that is treated as a separate trust pursuant to § 641(c) of the Internal Revenue Code [26 U.S.C. § 641(c)].