B — Business Zone. The Business Zone shall comprise the area on both sides of Long Beach Boulevard to a depth of 100 feet from the street lines of the Boulevard between the center line of South Third Street and the centerline of Twenty-Fifth Street, except in Blocks 17, 18, 24 and 25, in which four blocks the depth of the Business Zone shall be 130 feet northwest of the northwest street line of the Boulevard, as shown on the zone map.