(d)). (6) Business interest income For purposes of this subsection, the term business interest income means the amount of interest includible in the gross income of the taxpayer for the taxable year which is properly allocable to a trade or business. Such term shall not include investment income (within the meaning of subsection (d)). (7) Trade or business For purposes of this subsection— (A) In general The term trade or business shall not include— (i) the trade or business of performing services as an employee, (ii) any electing real property trade or business, (iii) any electing farming business, or (iv) the trade or business of the furnishing or sale of— (I) electrical energy, water, or sewage disposal services, (II) gas or steam through a local distribution system, or (III) transportation of gas or steam by pipeline, if the rates for such furnishing or sale, as the case may be, have been established or approved by a State or political subdivision thereof, by any agency or instrumentality of the United States, by a public service or public utility commission or other similar body of any State or political subdivision thereof, or by the governing or ratemaking body of an electric cooperative. (B) Electing real property trade or business For purposes of this paragraph, the term electing real property trade or business means any trade or business which is described in section 469(c)(7)(C) and which makes an election under this subparagraph. Any such election shall be made at such time and in such manner as the Secretary shall prescribe, and, once made, shall be irrevocable. (C) Electing farming business For purposes of this paragraph, the term electing farming business means a farming business (as defined in section 263A(e)(4)) which makes an election under this subparagraph. Any such election shall be made at such time and in such manner as the Secretary shall prescribe, and, once made, shall be irrevocable. (8) Adjusted taxable income For purposes of this subsection, the term adjusted taxable income means the