Solving a chemistry problem

3. For the polarographic determination of Mn (II), a calibration graph was constructed: aliquot parts of Val. a solution of Mn(II) salt with a concentration of 1•10-4 mol/l was diluted with a buffer solution to 25 ml and polarograms were obtained. The following data was obtained:
Val. (Mn II), ml 1.0 2.0 3.0 4.0 5.0 6.0

h, mm 9 16
26.5 35 41 54

A sample of the alloy weighing 0.5000 g containing manganese was dissolved in 100 ml of HNO3, 5.0 ml of the resulting solution was taken and diluted with the same buffer solution to 25 ml. During polarography, a wave height of 32.7 mm was obtained. Calculate the mass fraction of Mn in the alloy.