-- 10
SELECT
c.countrykey, c.countryname
FROM orderheader oh
INNER JOIN country c ON oh.countrykey = c.countrykey
INNER JOIN orderstatus os ON oh.orderstatuskey=os.orderstatuskey
WHERE os.orderstatusname like 'Finished'
GROUP BY c.countrykey, c.countryname
HAVING COUNT(*) =
(
 SELECT DISTINCT
 MAX(orders)
 FROM
 (
 SELECT DISTINCT
 COUNT(*) orders
 FROM orderheader oh
 INNER JOIN orderstatus os ON oh.orderstatuskey=os.orderstatuskey
 WHERE os.orderstatusname like 'Finished'
 GROUP BY oh.countrykey
 )
);