A 47-year-old man complains of weakness and dizziness. Half a year ago he underwent a gastric resection. Blood test: Hb – 80g/L, erythrocytes- 3.5 x 1012/l, color index – 0.69, ESR – 15mm/hr, serum iron – 5.4 mcmol/L, erythrocyte hypochromia. What type of anemia is the most likely in this patient?