Consider the following premises. For all x_18, x_18 will play tennis. For all x_18, x_18 will play tennis if and only if x_18 is a scientist. For all x_18, if x_18 cooks, then x_18 is a scientist. Can we infer the following from them? If we can, name the inference rule being used: Susan is not a scientist.
 From the fact that for all x_18, x_18 will play tennis if and only if x_18 is a scientist we can infer that for all x_18, if x_18 plays tennis, then x_18 is a scientist via universal biconditional elimination. From the fact that for all x_18, x_18 will play tennis we can infer that for all x_18, x_18 will play tennis or x_18 will cook via universal addition. Finally, from the fact that for all x_18, if x_18 plays tennis, then x_18 is a scientist, that for all x_18, if x_18 cooks, then x_18 is a scientist, and that for all x_18, x_18 will play tennis or x_18 will cook we can infer that for all x_18, x_18 is a scientist via universal disjunction elimination, which contradicts that Susan is not a scientist. Therefore, the answer is no.