instruction: what is the average hospital cost that involves a procedure, called stress ulcer treatment - antacids until 2104?
response: SELECT AVG(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 treatment.patientunitstayid FROM treatment WHERE treatment.treatmentname = 'stress ulcer treatment - antacids')) AND STRFTIME('%y', cost.chargetime) <= '2104' GROUP BY cost.patienthealthsystemstayid) AS t1