Consider the following premises. For all x_3, x_3 is an astronaut if and only if x_3 is a poet. For all x_3, if x_3 were a server, then x_3 is a poet. For all x_3, x_3 is a server or x_3 is an astronaut. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_3 for which x_3 is not a poet.
 From the fact that for all x_3, x_3 is an astronaut if and only if x_3 is a poet we can infer that for all x_3, if x_3 were an astronaut, then x_3 is a poet via universal biconditional elimination. Finally, from the fact that for all x_3, if x_3 were a server, then x_3 is a poet, that for all x_3, if x_3 were an astronaut, then x_3 is a poet, and that for all x_3, x_3 is a server or x_3 is an astronaut we can infer that for all x_3, x_3 is a poet via universal disjunction elimination, which contradicts that There is at least one x_3 for which x_3 is not a poet. Therefore, the answer is no.