select h.hacker_id, MIN(h.Name)
from Hackers h
join submissions s on h.hacker_id = s.hacker_id
join challenges c on c.challenge_id = s.challenge_id
join difficulty d on s.score=d.score
where d.difficulty_level=c.difficulty_level  
group by h.hacker_id
having count(*)>1
order by count(*) desc, 1