Consider the following premises. Charles is a mechanic if and only if it is windy. If Sarah were a bartender, then Charles is a mechanic. If it is windy, then Sarah is a bartender. Can we infer the following from them? If we can, name the inference rule being used: If is not true that it is windy if and only if Charles is a mechanic.
 From the fact that if it is windy, then Sarah is a bartender, and that if Sarah were a bartender, then Charles is a mechanic we can infer that if it is windy, then Charles is a mechanic via transitivity. From the fact that Charles is a mechanic if and only if it is windy we can infer that if Charles were a mechanic, then it is windy via biconditional elimination. Finally, from the fact that if it is windy, then Charles is a mechanic, and that if Charles were a mechanic, then it is windy we can infer that it is windy if and only if Charles is a mechanic via biconditional introduction, which contradicts that If is not true that it is windy if and only if Charles is a mechanic. Therefore, the answer is no.