what was the first dose of soln on their last hospital encounter, prescribed to patient 94316?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 94316 and admissions.dischtime is not null order by admissions.admittime desc limit 1 ) and prescriptions.drug = 'soln' order by prescriptions.startdate asc limit 1