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 a sailor, then Elisabeth is poor. Susan is driving a car. If Elisabeth were poor, then Joseph is a sailor. Joseph is not a sailor.
Elisabeth is not poor can be inferred via the modus tollens rule. Susan is driving a car and Joseph is not a sailor can be inferred via the conjunction rule. Joseph is not a sailor and Susan is driving a car can be inferred via the conjunction rule. Joseph is a sailor if and only if Elisabeth is poor can be inferred via the biconditional introduction rule. Elisabeth is poor if and only if Joseph is a sailor can be inferred via the biconditional introduction rule.