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

parameters
offset a	slope b
-1.3328e-06	7.75333e-05

Covariance matrix
1.43638e-14	-6.08263e-13
-6.08263e-13	2.61647e-11

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.15	1.75523e-06	8.61194e-08	Ba133
80.98	4.29764e-07	1.51698e-08	Ba133
