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 y_4, y_4 is not a mechanic. There is at least one y_4 for which y_4 is a mechanic if and only if y_4 will listen to a song.
There is at least one y_4 for which if y_4 were a mechanic, then y_4 is listening to a song can be inferred via the existential biconditional elimination rule. There is at least one y_4 for which if y_4 listens to a song, then y_4 is a mechanic can be inferred via the existential biconditional elimination rule. There is at least one y_4 for which y_4 will not listen to a song can be inferred via the existential biconditional elimination rule.