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 z_2, z_2 will not play squash. There is at least one z_2 for which if z_2 were fast, then z_2 is listening to a song. For all z_2, z_2 is fast if and only if z_2 will play squash. For all z_2, if z_2 listens to a song, then z_2 is fast.
There is at least one z_2 for which z_2 is fast if and only if z_2 will listen to a song can be inferred via the existential biconditional introduction rule. There is at least one z_2 for which z_2 will listen to a song if and only if z_2 is fast can be inferred via the existential biconditional introduction rule. For all z_2, if z_2 were fast, then z_2 is playing squash can be inferred via the universal biconditional elimination rule. For all z_2, if z_2 plays squash, then z_2 is fast can be inferred via the universal biconditional elimination rule. For all z_2, z_2 is not fast can be inferred via the universal biconditional elimination rule.