What is the maximum sweep volume of a car that costs less than $30000?
cost less than $30000 refers to price < 30000; the maximum sweep volume = max(divide(displacement, cylinders)) where price < 30000
SELECT MAX(T1.displacement / T1.cylinders) FROM data AS T1 INNER JOIN price AS T2 ON T1.ID = T2.ID WHERE T2.price < 30000