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: It is not sunny. Susan is drinking water or it is not snowing. If it is sunny, then Susan is drinking water. If Susan drinks water, then it is sunny.
Susan is not drinking water can be inferred via the modus tollens rule. If it snows, then Susan is drinking water can be inferred via the rewriting rule. It is sunny if and only if Susan is drinking water can be inferred via the biconditional introduction rule. Susan is drinking water if and only if it is sunny can be inferred via the biconditional introduction rule.