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: If Joseph were an artist, then Thomas is an office clerk. Joseph is not an artist. If Thomas were an office clerk, then Joseph is an artist.
Thomas is not an office clerk can be inferred via the modus tollens rule. Joseph is an artist if and only if Thomas is an office clerk can be inferred via the biconditional introduction rule. Thomas is an office clerk if and only if Joseph is an artist can be inferred via the biconditional introduction rule.