Consider the following premises. It is cold or Richard is drinking water. For all x_16, x_16 will drink water if and only if x_16 is a scientist. It is not cold. Can we infer the following from them? If we can, name the inference rule being used: Richard is not a scientist.
 From the fact that for all x_16, x_16 will drink water if and only if x_16 is a scientist we can infer that Richard is drinking water if and only if Richard is a scientist via universal instantiation. From the fact that Richard is drinking water if and only if Richard is a scientist we can infer that if Richard drinks water, then Richard is a scientist via biconditional elimination. From the fact that it is cold or Richard is drinking water, and that it is not cold we can infer that Richard is drinking water via disjunctive syllogism. Finally, from the fact that if Richard drinks water, then Richard is a scientist, and that Richard is drinking water we can infer that Richard is a scientist via modus ponens, which contradicts that Richard is not a scientist. Therefore, the answer is no.