In the reaction 5Fe^{2+} + MnO_4^{-} + 8H^{+} → 5Fe^{3+} + Mn^{2+} + 4H_2O, how many grams of Fe^{2+} will be oxidized by 1000 mL of a 1 M KMnO_4 solution? (Atomic mass of Fe = 55.85 g mol⁻¹)