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: David is an electrician. David is an electrician if and only if Robert is a writer.
If David were an electrician, then Robert is a writer can be inferred via the biconditional elimination rule. If Robert were a writer, then David is an electrician can be inferred via the biconditional elimination rule.