The Y_X − M₅₀₀ and Y_X − M₂₅₀₀ scaling relations for a sample of eight relaxed galaxy clusters. The blue data points and curves correspond to the measurements obtained from a uniform helium abundance case and red data points and curves correspond to the measurements obtained from a helium sedimentation model. The dashed lines show the best fit power law relation and solid curves show the 90% confidence levels.