A hemoglobin molecule can bind four O2 molecules. Assume that is the energy of each bound O2, relative to O2 at rest at infinite

A hemoglobin molecule can bind four O2 molecules. Assume that ε is the energy of each bound O2, relative to O2 at rest at infinite distance. Let λ denote the absolute activity exp (μ/τ) of the free O2 (in solution)
(a) What is the probability that one and only one O2 is absorbed on a hemoglobin molecule? Sketch the result qualitatively as a function of λ.
(b) What is the probability that four and only four O2 are adsorbed? Sketch this result also.