For buildings with professional, governmental or business offices or laboratory establishments: if floor area is less than 8,000 square feet, none; if floor area amounts to between 8,000 and 25,000 square feet, one berth; for each additional 25,000 square feet or major fraction thereof up to 100,000 square feet, one additional berth; for each additional 50,000 square feet or major fraction thereof, one additional berth.