Consider the following premises. For all x_7, x_7 is a bartender if and only if x_7 will drive a car. There is at least one x_7 for which x_7 will go running if and only if x_7 is a server. For all x_7, x_7 is not a bartender. For all x_7, x_7 will drive a car if and only if x_7 will go running. Can we infer the following from them? If we can, name the inference rule being used: For all x_7, x_7 is a server.
 From the fact that for all x_7, x_7 is a bartender if and only if x_7 will drive a car, and that for all x_7, x_7 is not a bartender we can infer that for all x_7, x_7 will not drive a car via universal biconditional elimination. From the fact that for all x_7, x_7 will drive a car if and only if x_7 will go running, and that for all x_7, x_7 will not drive a car we can infer that for all x_7, x_7 will not go running via universal biconditional elimination. Finally, from the fact that there is at least one x_7 for which x_7 will go running if and only if x_7 is a server, and that for all x_7, x_7 will not go running we can infer that there is at least one x_7 for which x_7 is not a server via existential biconditional elimination, which contradicts that For all x_7, x_7 is a server. Therefore, the answer is no.