Question: Among the complaints received in year 2015, what is total number of complaints timely response and closed with an explanation?
SQL: SELECT COUNT(T1.`Complaint ID`) FROM callcenterlogs AS T1 INNER JOIN events AS T2 ON T1.`Complaint ID` = T2.`Complaint ID` WHERE strftime('%Y', T1.`Date received`) = '2015' AND T2.`Timely response?` = 'Yes' AND T2.`Company response to consumer` = 'Closed with explanation'