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

parameters
offset a	slope b
-1.13527e-06	6.58406e-05

Covariance matrix
1.07265e-14	-4.55207e-13
-4.55207e-13	1.96067e-11

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.16	1.4856e-06	7.45244e-08	Ba133
80.97	3.61368e-07	1.27507e-08	Ba133
