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: There is at least one y_4 for which y_4 will not play squash. For all y_4, y_4 will play squash if and only if y_4 will listen to a song. For all y_4, y_4 will listen to a song if and only if y_4 will go running.
For all y_4, if y_4 plays squash, then y_4 is listening to a song can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 listens to a song, then y_4 is running can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 listens to a song, then y_4 is playing squash can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 goes running, then y_4 is listening to a song can be inferred via the universal 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.