Puzzle: Does Occasional Simulation Enable Cooperation? (Puzzle in honor of Joe Halpern's 70th birthday)

Please send solutions to the author by e-mail, with the title of this puzzle in the subject header. By agreement with the editors, the best solution will be published in the next issue of SIGecom Exchanges, provided that that solution is of sufficiently high quality. Quality is judged by the author, taking into account at least soundness, completeness, and clarity of exposition. (Incidentally, there is another birthday puzzle for which we still need a solution [1]!)