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