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_4, z_4 will cook if and only if z_4 will play squash. For all z_4, if z_4 plays squash, then z_4 is cooking. Mary is not playing squash.
For all z_4, if z_4 cooks, then z_4 is playing squash can be inferred via the universal biconditional elimination rule. For all z_4, if z_4 plays squash, then z_4 is cooking can be inferred via the universal biconditional elimination rule.