The State Board of Education may sell any particular unit of such pupil-transportation equipment to an eligible school district, at any time after such unit has been leased for one (1) fiscal year, for an amount not less than the original total cost of such unit less rentals actually paid for the use of such unit; provided, however, in so selling any such unit, preference shall be given to the school district leasing such unit during the then preceding fiscal year.
Okla. Stat. tit. 70, § 9-114