Where a lot is situated between two lots, each of which is developed with a principal building which has a nonconforming front yard setback, the minimum front yard setback requirement for such lot may be the average of the front yards supplied with respect to the existing nonconforming buildings on the said adjacent lots.

Where a lot adjoins one lot developed as described above and a vacant lot, the minimum front yard setback requirement for such lot may be the average of the nonconforming front yard setback of the developed lot and the required front yard setback for the zone.

Where in any given block there exists a prevailing uniformity in the alignment and setback of existing buildings in which the front yard setbacks are greater or less than required, then, in that event, any new building in such block shall conform to such established alignment and setback.