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: Barbara is not running. Barbara is running or it is not snowing. It is snowing if and only if Karen is an astronaut.
It is not snowing can be inferred via the disjunctive syllogism rule. If it snows, then Barbara is running can be inferred via the rewriting rule. If it snows, then Karen is an astronaut can be inferred via the biconditional elimination rule. If Karen were an astronaut, then it is snowing can be inferred via the biconditional elimination rule.