Translate the following question to SQL: What are the speeds of the longest roller coaster?

Schema: CREATE TABLE roller_coaster (
    Roller_Coaster_ID INT   PRIMARY KEY,
    Name TEXT,
    Park TEXT,
    Country_ID INT,
    Length REAL,
    Height REAL,
    Speed TEXT,
    Opened TEXT,
    Status TEXT,
    UNIQUE (Roller_Coaster_ID),
    FOREIGN KEY (Country_ID) REFERENCES country(Country_ID)
);

CREATE TABLE country (
    Country_ID INT   PRIMARY KEY,
    Name TEXT,
    Population INT,
    Area INT,
    Languages TEXT,
    UNIQUE (Country_ID)
);
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SELECT Speed FROM roller_coaster ORDER BY LENGTH DESC LIMIT 1
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