Consider the following premises. For all x_18, x_18 is a doctor. Robert is playing a game and Karen is a mechanic. Can we infer the following from them? If we can, name the inference rule being used: Robert is not playing a game.
 From the fact that for all x_18, x_18 is a doctor we can infer that Robert is a doctor via universal instantiation. Finally, from the fact that Robert is playing a game and Karen is a mechanic we can infer that Robert is playing a game via simplification, which contradicts that Robert is not playing a game. Therefore, the answer is no.