15

SELECT rankedCurrencies.ContinentCode, rankedCurrencies.CurrencyCode, rankedCurrencies.Count
FROM (
SELECT c.ContinentCode, c.CurrencyCode, COUNT(c.CurrencyCode) AS [Count], DENSE_RANK() OVER (PARTITION BY c.ContinentCode ORDER BY COUNT(c.CurrencyCode) DESC) AS [rank]
FROM Countries AS c
GROUP BY c.ContinentCode, c.CurrencyCode) AS rankedCurrencies
WHERE rankedCurrencies.rank = 1 and rankedCurrencies.Count > 1