user: Question: What is the average speed for ships before 1974 with over 1.73 passengers?
Columns: ['Ship name', 'Year', 'Length', 'Width', 'Passengers', 'Vessels', 'Speed']
Types: ['text', 'real', 'text', 'text', 'real', 'real', 'real']
Sample row: ['Mytilene', 1973.0, '138,3 m', '22,4 m', 1.73, 225.0, 20.0]
SQL:

assistant: SELECT AVG("Speed") FROM "Table" WHERE "Year" < 1974.0 AND "Passengers" > 1.73;