Calculate the average age of clients whose response is "Closed with relief".
average age = avg(age where Company response to consumer = 'Closed with relief'); response "Closed with relief" refers to Company response to consumer = 'Closed with relief'
SELECT AVG(T1.age) FROM client AS T1 INNER JOIN events AS T2 ON T1.client_id = T2.Client_ID WHERE T2.`Company response to consumer` = 'Closed with relief'