Database: address
Question: What is the elevation of the city belonging to Hampden, Massachusetts?
SQL: SELECT T3.elevation FROM state AS T1 INNER JOIN country AS T2 ON T1.abbreviation = T2.state INNER JOIN zip_data AS T3 ON T2.zip_code = T3.zip_code WHERE T1.name = 'Massachusetts' AND T2.county = 'HAMPDEN' GROUP BY T3.elevation