when was the last time patient 65401 was prescribed medication through the ed route in 10/2105?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 65401 ) and prescriptions.route = 'ed' and strftime('%y-%m',prescriptions.startdate) = '2105-10' order by prescriptions.startdate desc limit 1