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 Linda were a lawyer, then Robert is playing a game. Karen is not working. If Robert plays a game, then Karen is working. If Karen works, then Robert is playing a game. If Jennifer were a doctor, then Linda is a lawyer.
Robert is not playing a game can be inferred via the modus tollens rule. If Linda were a lawyer, then Karen is working can be inferred via the transitivity rule. If Jennifer were a doctor, then Robert is playing a game can be inferred via the transitivity rule. Robert is playing a game if and only if Karen is working can be inferred via the biconditional introduction rule. Karen is working if and only if Robert is playing a game can be inferred via the biconditional introduction rule.