If we find the corresponding y value for the black curve, the pure hemoglobin, the value is around 0.9. And that means 90% of the hemoglobin, the pure hemoglobin will be saturated with oxygen. And so that means a difference of 98 -90. Or 8% of that oxygen will be unloaded to the tissues. Now, if we compare to the hemoglobin as it is present inside red blood cells. The corresponding y value is around zero point 32 so that means 98 -32 gives us 66%.