Question: How many cities which belong to New Jersey have transported weight greater than 20000?
SQL: SELECT COUNT(*) FROM ( SELECT T2.city_id AS CITYID FROM shipment AS T1 INNER JOIN city AS T2 ON T1.city_id = T2.city_id WHERE T2.state = 'New Jersey' GROUP BY T2.city_id HAVING SUM(T1.weight) > 20000 )