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

parameters
offset a	slope b
-4.11842e-06	0.000239834

Covariance matrix
1.49637e-13	-6.32359e-12
-6.32359e-12	2.71535e-10

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.16	5.44504e-06	2.7763e-07	Ba133
80.98	1.34062e-06	4.94665e-08	Ba133
