what is the maximum cost of a hospital that involves a drug named benztropine mesylate since 1 year ago?
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 = 'benztropine mesylate' ) and datetime(cost.chargetime) >= datetime(current_time,'-1 year') group by cost.hadm_id ) as t1