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, if z_4 were bored, then z_4 is playing a game. For all z_4, z_4 is not an electrician. For all z_4, if z_4 were an electrician, then z_4 is bored. For all z_4, if z_4 were bored, then z_4 is an electrician. For all z_4, if z_4 plays a game, then z_4 is bored.
For all z_4, z_4 is not bored can be inferred via the universal modus tollens rule. For all z_4, if z_4 were an electrician, then z_4 is playing a game can be inferred via the universal transitivity rule. For all z_4, if z_4 plays a game, then z_4 is an electrician can be inferred via the universal transitivity rule. For all z_4, z_4 is bored if and only if z_4 will play a game can be inferred via the universal biconditional introduction rule. For all z_4, z_4 is an electrician if and only if z_4 is bored can be inferred via the universal biconditional introduction rule. For all z_4, z_4 is bored if and only if z_4 is an electrician can be inferred via the universal biconditional introduction rule. For all z_4, z_4 will play a game if and only if z_4 is bored can be inferred via the universal biconditional introduction rule.