for X being non empty compact Subset of (TOP-REAL 2) holds
( (NW-corner X) `1 <= (N-min X) `1 & (NW-corner X) `1 <= (N-max X) `1 & (NW-corner X) `1 <= (NE-corner X) `1 & (N-min X) `1 <= (N-max X) `1 & (N-min X) `1 <= (NE-corner X) `1 & (N-max X) `1 <= (NE-corner X) `1 )