at retail, automotive fuel with a research octane number of 95 unless such person displays, in a manner specified in the rules promulgated under subsection (b), the total price per gallon of such fuel on any sign on which such person displays the price of the most-sold grade of automotive fuel of such person. (b) Rulemaking (1) In general Not later than 6 months after the date of the enactment of this Act, the Federal Trade Commission shall promulgate, in accordance with section 553 of title 5, United States Code, any rules necessary for the implementation and enforcement of this section. (2) Contents Such rules— (A) shall define retail and most-sold for the purposes of this section