user: Question: What was the average speed of Tony Stewart's winning Chevrolet Impala?
Columns: ['Season', 'Date', 'Winning Driver', 'Car #', 'Sponsor', 'Make', 'Team', 'Avg Speed', 'Margin of Victory']
Types: ['real', 'text', 'text', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [1993.0, 'July 11', 'Rusty Wallace', 2.0, 'Miller Genuine Draft', 'Pontiac Grand Prix', 'Penske Racing', 'mph (km/h)', '1.31 sec']
SQL:

assistant: SELECT "Avg Speed" FROM "Table" WHERE "Winning Driver" = 'Tony Stewart' AND "Make" = 'Chevrolet Impala';