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: Richard is an electrician if and only if Barbara is a poet. Robert is not a mechanic. John is a soldier or Richard is an electrician. If John were a soldier, then Robert is a mechanic.
John is not a soldier can be inferred via the modus tollens rule. If Richard were an electrician, then Barbara is a poet can be inferred via the biconditional elimination rule. If Barbara were a poet, then Richard is an electrician can be inferred via the biconditional elimination rule.