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 Charles were not a mechanic, then it is snowing. It is not cold. Joseph is drinking water. Charles is a mechanic if and only if it is cold.
It is not cold and Joseph is drinking water can be inferred via the conjunction rule. Joseph is drinking water and it is not cold can be inferred via the conjunction rule. If Charles were a mechanic, then it is cold can be inferred via the biconditional elimination rule. If it is cold, then Charles is a mechanic can be inferred via the biconditional elimination rule. Charles is not a mechanic can be inferred via the biconditional elimination rule.