2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123802We give in this paper an example of infinitary rational relation, accepted by a 2-tape Büchi automaton, which is Pi^0_3-complete in the Borel hierarchy. Moreover the example of infinitary rational relation given in this paper has a very simple structure and can be easily described by its sections.LogicComputational ComplexityLogic in Computer Sciencetext