what is the area (km ) when the rank is south africa and the population (2011) is more than 51,770,561?
CREATE TABLE table_14253 (
    "Rank" text,
    "Province" text,
    "Population (2011)" real,
    "Area (km\u00b2)" real,
    "Density (per km\u00b2)" real
)
SELECT AVG("Area (km\u00b2)") FROM table_14253 WHERE "Rank" = 'south africa' AND "Population (2011)" > '51,770,561'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: what is the area (km ) when the rank is south africa and the population (2011) is more than 51,770,561? ### Input: CREATE TABLE table_14253 (
    "Rank" text,
    "Province" text,
    "Population (2011)" real,
    "Area (km\u00b2)" real,
    "Density (per km\u00b2)" real
) ### Response: SELECT AVG("Area (km\u00b2)") FROM table_14253 WHERE "Rank" = 'south africa' AND "Population (2011)" > '51,770,561'