16. Solving a chemistry problem

5. A portion of the silver alloy weighing 2.157 g was dissolved and, after appropriate treatment, the volume of the solution was brought to 100.00 ml. Determine the mass fraction (%) of silver in the alloy, if the conductometric titration of 25.00 ml of this solution with 0.1200 M sodium chloride solution obtained the following data:
VNaCl, ml 16.0 18.0 19.0 19.5 19.9 20.0 20.1 20.5 21.0
R, Ohm 354 358 362 365 369 370 365 350 338