36. Solving a chemistry problem

5. A portion of the alloy, 2.157 g, was dissolved in acid and, after appropriate treatment, the volume of the solution was brought to 100 ml. Determine the percentage of silver in the alloy if, during potentiometric titration, 25.0 ml of the prepared solution of 0.13 N. NaCl solution obtained the following results:
V NaCl, ml 16.0 18.0 19.0 19.5 19.9 20.0 20.1 20.5 21.0
E, mV 689 670 652 634 549 518 441 401 383