Consider the following premises. For all x_6, x_6 will drink water if and only if x_6 is a poet. For all x_6, if x_6 were a poet, then x_6 is not a taxi driver. For all x_6, x_6 is a taxi driver. Can we infer the following from them? If we can, name the inference rule being used: For all x_6, x_6 will not drink water.
 From the fact that for all x_6, if x_6 were a poet, then x_6 is not a taxi driver, and that for all x_6, x_6 is a taxi driver we can infer that for all x_6, x_6 is not a poet via universal modus tollens. From the fact that for all x_6, x_6 will drink water if and only if x_6 is a poet we can infer that for all x_6, if x_6 drinks water, then x_6 is a poet via universal biconditional elimination. Finally, from the fact that for all x_6, if x_6 drinks water, then x_6 is a poet, and that for all x_6, x_6 is not a poet we can infer that for all x_6, x_6 will not drink water via universal modus tollens. Therefore, the answer is yes.