A 458g sample containing $M{n}_3{O}_4$ was dissolved and all manganese was converted to $M{n}^{2+}$.          In the presence of fluoride $ion,M{n}^{2+}$ is titrated with 3 lit of $KMn{O}_4$ solution (which was 1.25N against oxalate in acidic medium), both reactants being converted to a complex of Mn(III). What was the % of $M{n}_3{O}_4$ in the sample? (Mn=55)