Saturation and the oxygen given up

You will use a model of the oxygen dissociation curve. It gives the saturation of haemoglobin for a pO$_2$ and a value of $P_{50}$. Then you will find how much oxygen the blood gives up under three conditions.

The idea. The model is $\text{saturation} = 100 \times \dfrac{p^{2.7}}{P_{50}^{2.7} + p^{2.7}}$, where $p$ is the pO$_2$.

Your tasks.

1. Finish saturation. It gives the saturation in per cent from po2 and p50.
2. Finish given_up. It gives the fall in saturation from the lungs, at 104 mm Hg, to the tissues, at 40 mm Hg.
3. Set best to the name of the condition in which the blood gives up the most.