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, y is not a lawyer. For all y, if y were a carpenter, then y is an electrician. For all y, if y were an electrician, then y is a carpenter. For all y, if y were a carpenter, then y is a lawyer.
For all y, y is not a carpenter can be inferred via the universal modus tollens rule. For all y, if y were an electrician, then y is a lawyer can be inferred via the universal transitivity rule. For all y, y is a carpenter if and only if y is an electrician can be inferred via the universal biconditional introduction rule. For all y, y is an electrician if and only if y is a carpenter can be inferred via the universal biconditional introduction rule.