Calculate the mass of the sample, which contains about 65% MnO2, that after interaction with 50,00 ml of 0.1 M H2C2O4 (feq = 1/2), the excess of it should be titrated with 25.00 ml of KMnO4 solution (1.00 ml of KMnO4 solution is equivalent to 1, 05 ml of H2C2O4 solution)