Question: List the educationnum and response of customers within the age of 20 to 30 that has the highest number of inhabitants among the group.
SQL: SELECT T1.EDUCATIONNUM, T2.RESPONSE FROM Customers AS T1 INNER JOIN Mailings1_2 AS T2 ON T1.ID = T2.REFID INNER JOIN Demog AS T3 ON T1.GEOID = T3.GEOID WHERE T1.age >= 20 AND T1.age <= 30 ORDER BY T3.INHABITANTS_K DESC LIMIT 1