Considering the text provided, what is the main limitation of the alternating offers model for studying real-world negotiations?


a) The model does not take into account the relative cost of waiting, which can be trivial in some negotiations.
b) The model assumes that negotiations never break down and that all results are Pareto efficient.
c) The model cannot incorporate external options in the same way as in the Nash model.
d) The model assumes that negotiators have the same discount rate, which is not realistic in many situations.