when did patient 10855 receive a prescription for the last time since 11/2102, via tt route?
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 10855 ) and prescriptions.route = 'tt' and strftime('%y-%m',prescriptions.startdate) >= '2102-11' order by prescriptions.startdate desc limit 1