arc. a tournament. T then models a round robin tournament. the verices of T and the teams in the round robin tournament and (u,v) is an arc in T if team u defat team u (Ties are not permitted.) Recall that two digraphs D and D' are isomorphic, written as D D', If there exists a bijectvie function ....... such that(u,v) ... If and only if ..... such a function is called an isomorphism there is only one tournament of order 1 and only one tournament of order 2(up to isomorphism) there are two tournaments of order 3and four tournaments of order 4. the tournaments of order 4 or less are shown in figure 7.9. there are also 12 tournaments of order 5.based on this information, it probably cornes as a great surprise to learn that there are over 154billion tournaments of order 12