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 overcast. It is snowing. If Elisabeth drinks water, then it is overcast. Elisabeth is drinking water if and only if it is overcast.
Elisabeth is not drinking water can be inferred via the modus tollens rule. It is not overcast and it is snowing can be inferred via the conjunction rule. It is snowing and it is not overcast can be inferred via the conjunction rule. If Elisabeth drinks water, then it is overcast can be inferred via the biconditional elimination rule. If it is overcast, then Elisabeth is drinking water can be inferred via the biconditional elimination rule. Elisabeth is not drinking water can be inferred via the biconditional elimination rule.