On interior lots: 0.50 of the first 4,000 square feet of lot area; 0.20 of the lot area in excess of the first 4,000 square feet which is less than 100 feet from the street on which the lot abuts; and 0.10 of the lot area in excess of the first 4,000 square feet which is farther than 100 feet from said street. To the extent required, all of the area of the lot within 100 feet of the street on which the lot abuts must be included in the calculation of the first 4,000 square feet of lot area.