What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all x_6, x_6 is not sad or x_6 will go running. For all x_6, if x_6 goes running, then x_6 is playing tennis. For all x_6, x_6 will play tennis if and only if x_6 will listen to a song. There is at least one x_6 for which x_6 is sad or x_6 will listen to a song.
There is at least one x_6 for which x_6 will listen to a song or x_6 will go running can be inferred via the existential resolution rule. For all x_6, if x_6 plays tennis, then x_6 is listening to a song can be inferred via the universal biconditional elimination rule. For all x_6, if x_6 listens to a song, then x_6 is playing tennis can be inferred via the universal biconditional elimination rule.