SELECT @lastWeekMondayTime AS started, @lastWeekFridayTime AS ended
FROM (
    SELECT @lastWeek := DATE_ADD(CURDATE(), INTERVAL -1 WEEK),
           @lastWeekMonday := DATE_ADD(@lastWeek, INTERVAL (-WEEKDAY(@lastWeek)) DAY),
           @lastWeekFriday := DATE_ADD(@lastWeekMonday, INTERVAL (+6) DAY),
           @lastWeekMondayTime := ADDTIME(DATE(@lastWeekMonday), '00:00:00'),
           @lastWeekFridayTime := ADDTIME(DATE(@lastWeekFriday), '23:59:59')
) t