What are the ranks of captains that are both in the Cutter and Armed schooner classes?
SELECT rank FROM captain WHERE CLASS  =  'Cutter' INTERSECT SELECT rank FROM captain WHERE CLASS  =  'Armed schooner'
SELECT rank FROM captain WHERE CLASS  =  'Cutter' INTERSECT SELECT rank FROM captain WHERE CLASS  =  'Armed schooner'
[{'Rank': 'Midshipman'}]