how much is the average cost for a hospital that contains ciprofloxacin hcl until 2101?
select avg(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 = 'ciprofloxacin hcl' ) and strftime('%y',cost.chargetime) <= '2101' group by cost.hadm_id ) as t1