In cases where a boundary line extends parallel to the short dimension of the block and no dimensions are shown, such boundary line shall be considered to be located:

(a)        in the case of C1-1, C4-1, C4-2 or C4-4 Districts, 200 feet from the nearest street within the district;

(b)        in the case of C1-2, C1-3, C2-1, C2-2, C2-3, C4-3 or C7 Districts, 150 feet from the nearest street within the district; and

(c)        in the case of all other districts, 100 feet from the nearest street within the district.