A sample of pure sodium oxalate weighing 0.2500 gram, when dissolved in dilute sulfuric acid solution requires 40.15 mL

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A sample of pure sodium oxalate weighing 0.2500 gram, when dissolved in dilute
sulfuric acid solution requires 40.15 mL of ceric sulfate solution to give a permanent
yellow color to the solution. What is the normality of the ceric sulfate solution? How
many grams of pure Ce(SO4)2 · 2(NH4)2SO4 · 2H2O should be dissolved in 500 mL of
solution in order to prepare a solution of this normality? If a sample of limonite weighing
0.3000 gram is dissolved in hydrochloric acid solution, the iron reduced by metallic silver
and then requires 25.03 mL of the above ceric sulfate solution, orthophenanthroline being
used as indicator, what percentage of ferric oxide is shown to be present in the limonite?