user: Question: What is the average weeks of a song with a larger than 3 position after 1977?
Columns: ['Year', 'Single', 'Chart', 'Position', 'Weeks on chart']
Types: ['real', 'text', 'text', 'real', 'real']
Sample row: [1977.0, '"Ma Baker"', 'UK single chart', 2.0, 13.0]
SQL:

assistant: SELECT AVG("Weeks on chart") FROM "Table" WHERE "Position" > 3.0 AND "Year" > 1977.0;