50. Solving a chemistry problem

230. When conducting a quantitative analysis of a sample containing nickel, using the external standard method, four standard samples were used to construct a calibration graph in the coordinates Nov / Next.st - СNi. To obtain reliable data, each standard sample and sample was measured 3 times. Measurement data are shown in the table:
СNi sample, % N1(Ni) N2(Ni) N3(Ni)
1st standard 0.80 23700 23520 23350
2nd standard 1.20 34943 35155 35695
3rd standard 1.45 40840 40886 40990
4th standard 2.40 68200 69801 69776
Sample X 38007 39750 38810
External standard 46954 47038 46684
Determine the nickel concentration in the sample.