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

parameters
offset a	slope b
-3.15797e-06	0.000184222

Covariance matrix
8.82398e-14	-3.73243e-12
-3.73243e-12	1.60374e-10

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.17	4.18359e-06	2.13193e-07	Ba133
80.98	1.03429e-06	3.764e-08	Ba133
