opportunity fund. (iii) Related party For purposes of subparagraph (A)(i), the related person rule of section 179(d)(2) shall be applied pursuant to subsection (e)(2) in lieu of the application of such rule in section 179(d)(2)(A). (3) Qualified rural opportunity zone business (A) In general The term qualified rural opportunity zone business means a trade or business— (i) in which substantially all of the tangible property owned or leased by the taxpayer is qualified rural opportunity zone business property (determined by substituting qualified rural opportunity zone business for qualified rural opportunity fund each place it appears in paragraph (2)(D)), (ii) which satisfies the requirements of paragraphs (2), (4), and (8) of section 1397C(b), and (iii) which is not described in section 144(c)(6)(B). (B) Special rule For purposes of subparagraph (A), tangible property that ceases to be a qualified rural opportunity zone business property shall continue to be treated as a qualified rural opportunity zone business property for the lesser of— (i) 5 years after the date on which such tangible property ceases to be so qualified, or (ii) the date on which such tangible property is no longer held by the qualified rural opportunity zone business. (4) Qualified rural opportunity zone (A) In general The term qualified rural opportunity zone means any population census tract which— (i) is located in a rural county, and (ii) is in persistent poverty (as determined by the Bureau of the Census as of the date of the enactment of this Act). (B) Rural county The term rural county means any county if more than 50 percent of the census blocks which comprise such county are rural blocks (as determined by the Bureau of the Census as of the date of the enactment of this Act). A rule similar to section 143(k)(2)(D) shall apply for purposes of the preceding sentence. (e) Applicable rules (1) Treatment of investments with mixed funds In the case of any investment in a qualified rural opportunity fund only a portion of which consists of