Why is electron affinity positive when the second electron is added to oxygen

An experimental procedure requires a 10 ml of acid to be dissolved

Consider the following reaction at equilibrium. 2co2 (g) 2co (g) + o2 (g) h° = -514 kj le châtelier's principle predicts that the equilibrium partial pressure of co (g) can be maximized by carrying out the reaction a. at high temperature and high pressure b. at high temperature and low pressure c. at low temperature and low pressure d. at low temperature and high pressure e. in the presence of solid carbon

What conclusion can you draw from this experiment about the components of the black ink?