Consider the following premises. William is working if and only if it is overcast. If it snows, then it is overcast. If it is overcast, then it is snowing. William is not working. Can we infer the following from them? If we can, name the inference rule being used: It is snowing.
 From the fact that if it snows, then it is overcast, and that if it is overcast, then it is snowing we can infer that it is snowing if and only if it is overcast via biconditional introduction. From the fact that William is working if and only if it is overcast, and that William is not working we can infer that it is not overcast via biconditional elimination. From the fact that it is snowing if and only if it is overcast we can infer that if it snows, then it is overcast via biconditional elimination. Finally, from the fact that if it snows, then it is overcast, and that it is not overcast we can infer that it is not snowing via modus tollens, which contradicts that It is snowing. Therefore, the answer is no.