a) For a lot held in single and separate ownership legally subdivided on the effective date of this Zoning Ordinance or any amendment thereto, and which does not fulfill the regulations for the minimum lot area and/or lot width for the Zoning District in which it is located, a building may be erected, altered and used on the lot, and the lot may be used for a conforming or permitted use providing the setback requirements are not less than the minimum specified herein for the Zoning District in which the lot is located.