what is the GDP of the city with the largest population.
CREATE TABLE city (
    city_id number,
    city text,
    hanzi text,
    hanyu_pinyin text,
    regional_population number,
    gdp number
)

CREATE TABLE match (
    match_id number,
    date text,
    venue text,
    score text,
    result text,
    competition text
)

CREATE TABLE hosting_city (
    year number,
    match_id number,
    host_city text
)

CREATE TABLE temperature (
    city_id number,
    jan number,
    feb number,
    mar number,
    apr number,
    jun number,
    jul number,
    aug number,
    sep number,
    oct number,
    nov number,
    dec number
)
SELECT gdp FROM city ORDER BY regional_population DESC LIMIT 1
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 GDP of the city with the largest population. ### Input: CREATE TABLE city (
    city_id number,
    city text,
    hanzi text,
    hanyu_pinyin text,
    regional_population number,
    gdp number
)

CREATE TABLE match (
    match_id number,
    date text,
    venue text,
    score text,
    result text,
    competition text
)

CREATE TABLE hosting_city (
    year number,
    match_id number,
    host_city text
)

CREATE TABLE temperature (
    city_id number,
    jan number,
    feb number,
    mar number,
    apr number,
    jun number,
    jul number,
    aug number,
    sep number,
    oct number,
    nov number,
    dec number
) ### Response: SELECT gdp FROM city ORDER BY regional_population DESC LIMIT 1