Consider the following premises. For all x_9, if x_9 makes tea, then x_9 is a lawyer. For all x_9, if x_9 were a sailor, then x_9 is making tea. For all x_9, if x_9 were a lawyer, then x_9 is making tea. There is at least one x_9 for which x_9 is not a lawyer. Can we infer the following from them? If we can, name the inference rule being used: For all x_9, x_9 is a sailor.
 From the fact that for all x_9, if x_9 were a lawyer, then x_9 is making tea, and that for all x_9, if x_9 makes tea, then x_9 is a lawyer we can infer that for all x_9, x_9 is a lawyer if and only if x_9 will make tea via universal biconditional introduction. From the fact that for all x_9, x_9 is a lawyer if and only if x_9 will make tea, and that there is at least one x_9 for which x_9 is not a lawyer we can infer that there is at least one x_9 for which x_9 will not make tea via existential biconditional elimination. Finally, from the fact that for all x_9, if x_9 were a sailor, then x_9 is making tea, and that there is at least one x_9 for which x_9 will not make tea we can infer that there is at least one x_9 for which x_9 is not a sailor via existential modus tollens, which contradicts that For all x_9, x_9 is a sailor. Therefore, the answer is no.