how many times patient 30671 had been prescribed potassium chl 20 meq / 1000 ml d5ns until 2104.
select count(*) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 30671 ) and prescriptions.drug = 'potassium chl 20 meq / 1000 ml d5ns' and strftime('%y',prescriptions.startdate) <= '2104'