All portions of a building or other structure shall comply with the height and setback regulations of a C2 District mapped within an R7A District, except that on Mermaid Avenue, and on intersecting streets within 50 feet of Mermaid Avenue, the street wall of a building shall be located on the street line and rise without setback to a minimum base height of 40 feet or the height of the building, whichever is less, except that:

(a)        to allow for corner articulation, the street wall may be located anywhere within an area bounded by intersecting street lines and lines 15 feet from and parallel to such street lines ; and

(b)        above the level of the second story, up to 30 percent of the aggregate width of street walls may be recessed, provided no recesses are located within 15 feet of an adjacent building or within 30 feet of the intersection of two street lines, except where corner articulation is provided as set forth in paragraph (b) of this Section.