what is the total acetaminophen dose that has been prescribed this month to patient 12927?
select sum(prescriptions.dose_val_rx) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 12927 ) and prescriptions.drug = 'acetaminophen' and datetime(prescriptions.startdate,'start of month') = datetime(current_time,'start of month','-0 month')