How many lengths of line 3 are given?
CREATE TABLE table_20512 (
    "Line" text,
    "Terminals" text,
    "Status" text,
    "Length" text,
    "Total number of stations" real,
    "Operator" text
)
SELECT COUNT("Length") FROM table_20512 WHERE "Line" = 'Line 3'
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: How many lengths of line 3 are given? ### Input: CREATE TABLE table_20512 (
    "Line" text,
    "Terminals" text,
    "Status" text,
    "Length" text,
    "Total number of stations" real,
    "Operator" text
) ### Response: SELECT COUNT("Length") FROM table_20512 WHERE "Line" = 'Line 3'