count the number of times that patient 10425 has been prescribed the sodium polystyrene sulfonate in 2104.
select count(*) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 10425 ) and prescriptions.drug = 'sodium polystyrene sulfonate' and strftime('%y',prescriptions.startdate) = '2104'