by striking 12-year period each place it appears and inserting 14-year period . (b) Effective date The amendment made by this section shall apply to coal produced after December 31, 2017. 109. Railroad track maintenance credit (a) In general Section 45G((f) is amended by striking January 1, 2018 and inserting January 1, 2020 . (b) Effective date (1) In general The amendment made by this section shall apply to expenditures paid or incurred during taxable years beginning after December 31, 2017. (2) Safe harbor assignments Assignments, including related expenditures paid or incurred, under paragraph (2) of section 45G(b) of the Internal Revenue Code of 1986 for any taxable year beginning on or after January 1, 2018, and before January 1, 2019, shall be treated as effective as of the close of such taxable year if made pursuant to a written agreement entered into no later than 90 days following the date of the enactment of this Act. 110. Energy efficient homes credit (a) In general Section 45L(g) is amended by striking December 31, 2017 and inserting December 31, 2019 . (b) Effective date The amendment made by this section shall apply to homes acquired after December 31, 2017. 111. Classification of certain race horses as 3-year property (a) In general Section 168(e)(3)(A)(i) is amended— (1) by striking January 1, 2018 in subclause (I) and inserting January 1, 2020 , and (2) by striking December 31, 2017 in subclause (II) and inserting December 31, 2019 . (b) Effective date The amendments made by this section shall apply to property placed in service after December 31, 2017. 112. Special allowance for second generation biofuel plant property (a) In general Section 168(l)(2)(D) is amended by striking January 1, 2018 and inserting January 1, 2020 . (b) Effective date The amendment made by this section shall apply to property placed in service after December 31, 2017. 113. Energy efficient commercial buildings deduction (a) In general Section 179D(h) is amended by striking December 31, 2017 and inserting December 31,