what was the enoxaparin sodium dose prescribed to patient 92846 last in 12/2105?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 92846 ) and prescriptions.drug = 'enoxaparin sodium' and strftime('%y-%m',prescriptions.startdate) = '2105-12' order by prescriptions.startdate desc limit 1