In carbon monoxide poisoning the CO replaces the O_2 adsorbed on hemoglobin (Hb) molecules in the blood. To show the effect, consider a model for which each adsorption site on a heme my be vacant or may be occupied with energy epsilon_A by one O_2 molecule or with energy epsilon_B by one CO molecule. Let N fixed heme sites be in equilibrium with O_2 and CO in the gas phases at concentrations such that the activities are lambda (O_2) = 1 times 10^-5 and lambda (CO) = 1 times 10^-7, all at body temperature 37 degree C. Neglect any spin multiplicity factors. (a) First consider the system in the absence of CO. Evaluate epsilon_A such that 90% of the Hb sites are occupied by of O_2. Express the answer in eV per O_2. (b) Now admit the CO under the specified conditions. Find epsilon_B such that only 10% of the Hb sites are occupied by O_2.