when was the last time patient 14836 had been prescribed lr and eucerin at the same time in 02/2105?
select t1.startdate from ( select admissions.subject_id, prescriptions.startdate from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'lr' and admissions.subject_id = 14836 and strftime('%y-%m',prescriptions.startdate) = '2105-02' ) as t1 join ( select admissions.subject_id, prescriptions.startdate from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'eucerin' and admissions.subject_id = 14836 and strftime('%y-%m',prescriptions.startdate) = '2105-02' ) as t2 on t1.subject_id = t2.subject_id where datetime(t1.startdate) = datetime(t2.startdate) order by t1.startdate desc limit 1