How many wheels do the long cars have?
long cars refers to len = 'long'
SELECT SUM(wheels) FROM cars WHERE len = 'long'
database name:db_id trains
cars table cars Cols: id dtype integer, train id dtype integer, position dtype integer, shape dtype text, length dtype text, sides dtype text, roof dtype text, wheels dtype integer, load_shape dtype text, load number dtype integer, 
trains table trains Cols: id dtype integer, direction dtype text, 
