Of 2010 est. with less than 171,750 and 2000 less than 131,714, what is the 1970 population average?
CREATE TABLE table_53636 (
    "City" text,
    "1970" real,
    "1980" real,
    "1990" real,
    "2000" real,
    "2010 est." real
)
SELECT AVG("1970") FROM table_53636 WHERE "2010 est." = '171,750' AND "2000" < '131,714'
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: Of 2010 est. with less than 171,750 and 2000 less than 131,714, what is the 1970 population average? ### Input: CREATE TABLE table_53636 (
    "City" text,
    "1970" real,
    "1980" real,
    "1990" real,
    "2000" real,
    "2010 est." real
) ### Response: SELECT AVG("1970") FROM table_53636 WHERE "2010 est." = '171,750' AND "2000" < '131,714'