Consider the following premises. Linda is drinking water. For all x_17, if x_17 were an electrician, then x_17 is drinking water. For all x_17, x_17 will drink water if and only if x_17 is an electrician. Can we infer the following from them? If we can, name the inference rule being used: For all x_17, x_17 is not an electrician.
 From the fact that for all x_17, x_17 will drink water if and only if x_17 is an electrician we can infer that for all x_17, if x_17 drinks water, then x_17 is an electrician via universal biconditional elimination. From the fact that for all x_17, if x_17 drinks water, then x_17 is an electrician, and that for all x_17, if x_17 were an electrician, then x_17 is drinking water we can infer that for all x_17, x_17 will drink water if and only if x_17 is an electrician via universal biconditional introduction. From the fact that Linda is drinking water we can infer that there is at least one x_17 for which x_17 will drink water via existential generalization. From the fact that for all x_17, x_17 will drink water if and only if x_17 is an electrician we can infer that for all x_17, if x_17 drinks water, then x_17 is an electrician via universal biconditional elimination. Finally, from the fact that for all x_17, if x_17 drinks water, then x_17 is an electrician, and that there is at least one x_17 for which x_17 will drink water we can infer that there is at least one x_17 for which x_17 is an electrician via existential modus ponens, which contradicts that For all x_17, x_17 is not an electrician. Therefore, the answer is no.