Marcelo de C. Griebeler Federal University of Rio Grande do Sul   Av. João Pessoa 52 sala 18D, 1º andar Porto Alegre, RS 90040-000 Brasil   griebeler.marcelo@gmail.com   https://sites.google.com/site/marcelodecgriebeler           JEL Areas: C6 : Mathematical Methods and Programming: General C7 : Game Theory and Bargaining Theory:General