72 percent of Oxygen is delivered to tissues at rest in cooperative binding.

Because the binding of oxygen to hemoglobin is cooperative, i.e. it exhibits positive cooperativity. This essentially means that the binding of the first molecule of oxygen facilitates the binding of the second, and so on.

Means there is no binding agreement. So free to play the strategy that is the optimal response to the other players actions.

The Bohr effect and cooperative binding of oxygen to hemoglobin is what makes it an effective carrier of oxygen from the lungs to the peripheral tissues. What is cooperative binding? The first oxygen bind less strongly to oxygen then does the subsequent oxygen molecules (hemoglobin has four binding zones for oxygen). This means that the binding curve is fairly steep. The Bohr effect is a negative effect on binding of oxygen by hemoglobin in the presence of increased pH. Since peripheral tissues release C02 it increases the local pH releasing the oxygen. After the first oxygen is released the remaining oxygen molecules are quickly disassociated from hemoglobin thus delivering the oxygen to the tissue in need of oxygen.

after one oxygen molecule binds to hemoglobin, it is easier for the other molecules to bind to the hemoglobin. this is known as cooperative binding.