Sonja Brangewitz University of Paderborn, Institute for Mathematical Economics, Bielefeld   Chair of Microeconomics Warburger Strasse 100 Paderborn, NRW 33098 Germany   sonja.brangewitz@wiwi.uni-paderborn.de             JEL Areas: C7 : Game Theory and Bargaining Theory:General D5 : General Equilibrium and Disequilibrium: General