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 late, then Richard is a doctor. It is snowing if and only if it is cloudy. Richard is not a doctor. It is late if and only if it is cloudy.
It is not late can be inferred via the modus tollens rule. If it snows, then it is cloudy can be inferred via the biconditional elimination rule. If it is late, then it is cloudy can be inferred via the biconditional elimination rule. If it is cloudy, then it is snowing can be inferred via the biconditional elimination rule. If it is cloudy, then it is late can be inferred via the biconditional elimination rule.