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 Jessica plays a game, then Susan is taking a plane. Susan is not taking a plane. Jessica is poor. Jessica is playing a game if and only if Susan is taking a plane.
Jessica is not playing a game can be inferred via the modus tollens rule. Susan is not taking a plane and Jessica is poor can be inferred via the conjunction rule. Jessica is poor and Susan is not taking a plane can be inferred via the conjunction rule. If Jessica plays a game, then Susan is taking a plane can be inferred via the biconditional elimination rule. If Susan takes a plane, then Jessica is playing a game can be inferred via the biconditional elimination rule. Jessica is not playing a game can be inferred via the biconditional elimination rule.