Toru Hokari Faculty of Economics, Keio University   Institute of Social Sciences University of Tsukuba 1-1-1 Ten'no-dai Tsukuba, Ibaraki 306-8571 Japan   hokari@econ.keio.ac.jp   http://member.social.tsukuba.ac.jp/hokari/           JEL Areas: C7 : Game Theory and Bargaining Theory:General C6 : Mathematical Methods and Programming: General