what's the maximum total cost of a hospital, including n-acetylprocainamide (napa) lab tests?
select max(t1.c1) from ( select sum(cost.cost) as c1 from cost where cost.hadm_id in ( select labevents.hadm_id from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'n-acetylprocainamide (napa)' ) ) group by cost.hadm_id ) as t1