Untitled

WITH (X:=SUMMARIZE ((Independence{country}) JOIN (Country{code, area} RENAME {code AS country}) JOIN (Encompasses{country, continent,percentage} )) BY {continent}:{cnt_countries:=COUNT(), sum_area:=SUM(area)}):
X UNION
EXTEND ((Continent{name} RENAME {name as continent}) MINUS X{continent}):{cnt_countries:=0, sum_area:=0.}