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const double x[22] = {28.98, 30.48, 30.98, 31.48, 31.98, 32.48, 32.98, 33.48, 33.98, 34.48, 34.98, 35.48, 35.98, 36.48, 36.98, 37.48, 37.98, 38.48, 38.98, 39.98, 40.98, 41.98};
   const double y[22] = {8.26, 7.26, 5.71, 6.15, 5.90, 5.15, 5.03, 4.30, 4.15, 3.30, 2.90, 2.71, 1.96, 1.57, 1.27, 0.90, 0.70, 0.47, 0.33, 0.20, 0.09, 0.06};
   const double w[22] = {2, 8, 2, 2, 2, 1, 11, 12, 24, 12, 6, 12, 21, 7, 74, 51, 159, 385, 171, 109, 18, 18}; //weights
   const double x0 = 37.74; //central value theorem

//model equation
//y = (1/2)*((x^2-2x0x+x0^2+4k^2)^(1/2) + x+x0) - x
//k^2 was calculated as 0.582018800686398, after using Solver in Excel where total error was a minimized sum of w(y-y0)^2
//constraint k^2>0;