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: Linda is a janitor if and only if Susan is not playing squash. Robert is bored. If Susan plays squash, then Robert is not bored.
Susan is not playing squash can be inferred via the modus tollens rule. If Linda were a janitor, then Susan is not playing squash can be inferred via the biconditional elimination rule. If Susan doesn't play squash, then Linda is a janitor can be inferred via the biconditional elimination rule.