and notifications by the end of the periods referred to in paragraphs (1)(A) and (1)(B), the Secretary shall designate and certify population census tracts that are low-income communities as qualified opportunity zones, as permitted by subsection (e). (c) Other definitions For purposes of this subsection— (1) Low-income communities The term low-income community has the same meaning as when used in section 45D(e). (2) Definition of periods (A) Consideration period The term consideration period means the 30-day period beginning on the date on which the Secretary receives notice under subsection (b)(1)(A)(i)(II), as extended under subsection (b)(1)(B). (B) Determination period The term determination period means the 90-day period beginning on the date of the enactment of the Investing in Opportunity Act , as extended under subsection (b)(1)(B). (d) Guidance for opportunity zone nominations When considering the nomination of qualified opportunity zones, governors should strive for the creation of qualified opportunity zones that are geographically concentrated and contiguous clusters of population census tracts and should give particular consideration to areas that— (1) are currently the focus of mutually reinforcing State, local, or private economic development initiatives to attract investment and foster startup activity, (2) have demonstrated success in geographically targeted development programs, such as promise zones, new market tax credit, empowerment zones, and renewal communities, and (3) have recently experienced significant layoffs due to business closures or relocations. (e) Number of designations (1) In general Except as provided by paragraph (2), the number of population census tracts in a State that may be designated as qualified opportunity zones under this section may not exceed 25 percent of the number of low-income communities in the State. (2) Exception If the number of low-income communities in a State is less than 100, then a total of 25 of such tracts may be designated as qualified opportunity