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 snowing if and only if it is cold. Charles is rich. If it is cold, then Charles is not rich. David is playing squash.
It is not cold can be inferred via the modus tollens rule. Charles is rich and David is playing squash can be inferred via the conjunction rule. David is playing squash and Charles is rich can be inferred via the conjunction rule. If it snows, then it is cold can be inferred via the biconditional elimination rule. If it is cold, then it is snowing can be inferred via the biconditional elimination rule.