Common Open Space. In addition to the amenities listed above, common open space shall include passive landscape, turf, paved areas and amenities subject to review and approval of the Planning Commission and City Council. A minimum of 20%, exclusive of roadways, street parkways, setback areas and private open space, of developments of three stories or less shall be devoted to open and recreational common area. Open space requirements for developments of four or more stories shall be determined by the City Council, but shall not be less than 10% of the site area and shall incorporate 5% of the open space on the rooftop.