how much nevirapine suspension was prescribed to patient 14990 last until 11/2104?
select prescriptions.dose_val_rx from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 14990 ) and prescriptions.drug = 'nevirapine suspension' and strftime('%y-%m',prescriptions.startdate) <= '2104-11' order by prescriptions.startdate desc limit 1