In any district with which is a combined "B" district, the following regulations shall apply as to building site areas, depths of front yards, and widths of side yards; provided, however, that such application shall not be made in any case in which any of the following regulations are less than corresponding regulations hereinbefore specified for any district with which is a combined "B" district.

(a)

Building Site Area Requirement: Shall be indicated by a number following the letter "B" in the district designation, which number shall represent the required area in thousands of square feet.

(b)

Side Yard Set-back Required: Ten percent of lot width on each side to a maximum requirement of fifteen feet, but in no case less than five feet for interior side yards or ten feet for side yards adjacent to streets on corner lots.