(a) where there are at least two other buildings on the same block face, the average of the greatest geodetic elevation of the contextual adjacent buildings, excluding ancillary structures;
(b) where there is only one other building on the same block face, the greatest geodetic elevation of such building, excluding ancillary structures; and
(c) where there is no other building on the same block face, a point 8.6 metres above the greatest geodetic elevation at grade on the subject parcel.