141. Solving a chemistry problem

A sample of a copper alloy weighing 0.7500 g was dissolved, the volume of the solution was brought to 250.0 ml, and 20.00 ml of the prepared solution was titrated potentiometrically with a sodium thiosulfate solution with a copper titer r (Na2S203 / Cu) = 0.01664 g / ml.
Construct titration curves in the coordinates E - V and dE / dV - V and calculate the mass fraction (%) of copper in the alloy according to the following data:
K (Na2S203), ml 1.50 1.90 2.00 2.05 2.08 2.10 2.12 2.15 2.20
E, mV 475 445 424 405 382 305 232 186 162