Used file for the fit: SDD_normalized-Efficiency_point-source_with-air_all-levels.csv

parameters
offset a	slope b
-1.74896e-06	0.000102355

Covariance matrix
2.60092e-14	-1.09981e-12
-1.09981e-12	4.72553e-11

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.15	2.32962e-06	1.15725e-07	Ba133
80.96	5.79357e-07	2.06247e-08	Ba133
