Lot area. The minimum total area for a planned office park shall be 15 acres, provided that subdivision of individual lots within a planned office park shall be permitted, subject to the other requirements and regulations of this chapter, including particularly but not limited to the requirement that development of a planned office park be pursuant to a single unified master development plan, and further provided that, when subdivision of individual lots within a planned office park is proposed, the average area of all lots within the office park shall be not less than five acres, and no single lot shall be less than three acres, and further provided that the entire tract to be developed as an office park shall be deed and otherwise restricted so as to prohibit further subdivision of individual lots thereafter.