Consider the following premises. If it is overcast, then James is a server. James is a server if and only if Karen is making tea. It is overcast. Can we infer the following from them? If we can, name the inference rule being used: Karen is not making tea.
 From the fact that if it is overcast, then James is a server, and that it is overcast we can infer that James is a server via modus ponens. From the fact that James is a server if and only if Karen is making tea we can infer that if James were a server, then Karen is making tea via biconditional elimination. Finally, from the fact that if James were a server, then Karen is making tea, and that James is a server we can infer that Karen is making tea via modus ponens, which contradicts that Karen is not making tea. Therefore, the answer is no.