what is the total dose cefepime that patient 30460 has been prescribed in 03/2104?
select sum(prescriptions.dose_val_rx) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 30460 ) and prescriptions.drug = 'cefepime' and strftime('%y-%m',prescriptions.startdate) = '2104-03'