Consider the following premises. Richard is a server. For all x_18, x_18 is a taxi driver. If William were a taxi driver, then Sarah is bored. Can we infer the following from them? If we can, name the inference rule being used: Sarah is not bored.
 From the fact that for all x_18, x_18 is a taxi driver we can infer that William is a taxi driver via universal instantiation. Finally, from the fact that if William were a taxi driver, then Sarah is bored, and that William is a taxi driver we can infer that Sarah is bored via modus ponens, which contradicts that Sarah is not bored. Therefore, the answer is no.