A 45 year old gentleman has undergone truncal vagatomy and pyloroplasty for bleeding duodenal ulcer seven years ago. Now he was intractable recurrent symptoms of peptic ulcer. All of the following suggest the diagnosis of Zolliner Ellison syndrome, except
Basal acid output of 15 meq/hour Serum gastrin value of 500 pg/ml Ulcers in proximal jejunum and lower end of esophagus Serum gastrin value of 200 pg/ml with secretion stimulation