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 it is cloudy, then it is late. If it is cloudy, then it is late. It is not cloudy. If it is late, then it is cloudy.
It is not late can be inferred via the modus tollens rule. It is cloudy if and only if it is late can be inferred via the biconditional introduction rule. It is cloudy if and only if it is late can be inferred via the biconditional introduction rule. It is late if and only if it is cloudy can be inferred via the biconditional introduction rule. It is late if and only if it is cloudy can be inferred via the biconditional introduction rule.