what's the minimum total cost of the hospital that involves a drug called insulin human regular last year?
select min(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 = 'insulin human regular' ) and datetime(cost.chargetime,'start of year') = datetime(current_time,'start of year','-1 year') group by cost.hadm_id ) as t1