And notice that the blue curve is shifted to the right with respect to that black curve. The question is why? So let's talk about how much of the hemoglobin actually unloads when it goes from the lungs to the exercising tissue in two cases, to see the difference between these two cases. So let's begin inside the lungs. So, inside the lungs, the partial pressure is about 100 mercury, and so the x value is 100. And if we find the corresponding y value on these two curves, we get the same value of about zero point 98.