when was the last mchc test that patient 14203 received until 05/2101?
select labevents.charttime from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'mchc' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 14203 ) and strftime('%y-%m',labevents.charttime) <= '2101-05' order by labevents.charttime desc limit 1