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: Susan is not running. For all x_23, x_23 will not cook. If Mary works, then Susan is running. If Susan goes running, then Mary is working. If Charles plays a game, then Thomas is cooking.
Mary is not working can be inferred via the modus tollens rule. Mary is working if and only if Susan is running can be inferred via the biconditional introduction rule. Susan is running if and only if Mary is working can be inferred via the biconditional introduction rule.