(a) Notwithstanding any other regulation, no yard area within twenty feet of any adjoining Residential Zoning District shall be used for accessory off-street parking or loading, for storage of materials or products, or for any manufacturing process.
(b) No primary entrance to any manufacturing use, nor any sign or show window visible from properties adjoining side or rear lot lines, shall be located within seventy-five feet of any Residential District boundary.