what was the last time since 12/07/2105 patient 30826 had a minimum arterial bp mean?
select chartevents.charttime from chartevents where chartevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 30826 ) ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'arterial bp mean' and d_items.linksto = 'chartevents' ) and strftime('%y-%m-%d',chartevents.charttime) >= '2105-12-07' order by chartevents.valuenum asc, chartevents.charttime desc limit 1