what amount of furosemide had been prescribed to patient 88659 in total since 09/2104?
select sum(prescriptions.dose_val_rx) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 88659 ) and prescriptions.drug = 'furosemide' and strftime('%y-%m',prescriptions.startdate) >= '2104-09'