what was the dose of ambisome that was prescribed since 02/2103 for the last time to patient 5561?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 5561 ) and prescriptions.drug = 'ambisome' and strftime('%y-%m',prescriptions.startdate) >= '2103-02' order by prescriptions.startdate desc limit 1