tell me the dose of ipratropium bromide that patient 60180 had been prescribed since 05/2104?
select sum(prescriptions.dose_val_rx) from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 60180 ) and prescriptions.drug = 'ipratropium bromide' and strftime('%y-%m',prescriptions.startdate) >= '2104-05'