what is the maximum total cost of a hospital that includes a drug named oxymetazoline since 2105?
select max(t1.c1) from ( select sum(cost.cost) as c1 from cost where cost.hadm_id in ( select prescriptions.hadm_id from prescriptions where prescriptions.drug = 'oxymetazoline' ) and strftime('%y',cost.chargetime) >= '2105' group by cost.hadm_id ) as t1