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

parameters
offset a	slope b
-1.95525e-06	0.00011192

Covariance matrix
2.9418e-14	-1.24875e-12
-1.24875e-12	5.37875e-11

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.15	2.50445e-06	1.23708e-07	Ba133
80.99	5.89733e-07	2.09496e-08	Ba133
