###HUMAN: what's the minimum cost of a hospital that includes a cortisol lab test until 4 years ago?, ###ASSISTANT: SELECT MIN(t1.c1) FROM (SELECT SUM(cost.cost) AS c1 FROM cost WHERE cost.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.patientunitstayid IN (SELECT lab.patientunitstayid FROM lab WHERE lab.labname = 'cortisol')) AND DATETIME(cost.chargetime) <= DATETIME(CURRENT_TIME(), '-4 year') GROUP BY cost.patienthealthsystemstayid) AS t1