when did the last lab test of patient 61751 happened in 11/2105?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 61751 ) and strftime('%y-%m',labevents.charttime) = '2105-11' order by labevents.charttime desc limit 1