instruction: how many hours has elapsed since patient 021-79544 stayed in ward 798 for the last time in the during the current hospital visit?
response: SELECT 24 * (STRFTIME('%j', CURRENT_TIME()) - STRFTIME('%j', patient.unitadmittime)) FROM patient WHERE patient.uniquepid = '021-79544' AND patient.wardid = 798 AND patient.hospitaldischargetime IS NULL ORDER BY patient.unitadmittime DESC LIMIT 1