What is the fewest number of silvers for teams with more than 21 gold and more than 4 bronze?
CREATE TABLE table_6284 (
    "Rank" text,
    "Institution" text,
    "Gold" real,
    "Silver" real,
    "Bronze" real
)
SELECT MIN("Silver") FROM table_6284 WHERE "Bronze" > '4' AND "Gold" > '21'
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 fewest number of silvers for teams with more than 21 gold and more than 4 bronze? ### Input: CREATE TABLE table_6284 (
    "Rank" text,
    "Institution" text,
    "Gold" real,
    "Silver" real,
    "Bronze" real
) ### Response: SELECT MIN("Silver") FROM table_6284 WHERE "Bronze" > '4' AND "Gold" > '21'