Walker leased a small lot to Keith for ten years at $1,000 a month, with a right for Keith to extend the lease for another ten-year term under the same terms except as to rent. The renewal option provided: Rental will be fixed in such amount as shall actually be agreed upon by the lessors and the lessee with the monthly rental fixed on the comparative basis of rental values as of the date of the renewal with rental values at this time reflected by the comparative business conditions of the two periods. Keith sought to exercise the renewal right and, when the parties were unable to agree on the rent, brought suit against Walker. Who prevails? Why?