In Exercise 9 you showed that the recognition problem and universal recognition problem for SL2 are decidable. We can use the structure of Myhill graphs to show that other problems for SL2 are decidable as well. For example, Finiteness of SL2 languages is decidable, which is to say,there is an algorithm that, given an SL2 automaton A, returns TRUE if L(A) is finite, FALSE otherwise.