A sample of ferrous sulphate and ferrous oxalate was dissolved in dil. H2SO4. The complete oxidation of reaction mixture required 40 mL of N/15KMnO4. After the oxidation, the reaction mixture was reduced by Zn and H2SO4. On again oxidation by same KMnO4, 25 mL were required. Calculate the ratio of Fe in ferrous sulphate and oxalate.