user: Question: What is the average year that the Belanger Motors had an Offenhauser L4 engine?
Columns: ['Year', 'Entrant', 'Chassis', 'Engine', 'Points']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1950.0, 'Blue Crown Spark Plug / Moore', 'Kurtis Kraft 2000', 'Offenhauser L4', 1.0]
SQL:

assistant: SELECT AVG("Year") FROM "Table" WHERE "Engine" = 'Offenhauser L4' AND "Entrant" = 'Belanger Motors';