For a building containing three or more dwelling units, the minimum land area shall be 40,000 square feet, but for each one-bedroom dwelling unit, the minimum land area shall be 2,000 square feet; for each two-bedroom dwelling unit, the minimum land area shall be 2,500 square feet; for each three-bedroom or more dwelling unit, the minimum land area shall be 3,500 square feet; and the minimum width of the lot at the front building line shall not be less than 165 feet or the distance necessary to provide the side yard specified below, whichever is greater. The minimum floor area per dwelling unit in a building containing three or more dwelling units shall be 500 square feet per dwelling unit.