Consider the following premises. There is at least one x_7 for which x_7 will make tea if and only if x_7 will write a letter. For all x_7, x_7 will drive a car if and only if x_7 will work. For all x_7, if x_7 writes a letter, then x_7 is working. For all x_7, x_7 will not drive a car. Can we infer the following from them? If we can, name the inference rule being used: For all x_7, x_7 will make tea.
 From the fact that for all x_7, x_7 will drive a car if and only if x_7 will work, 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 work via universal biconditional elimination. From the fact that for all x_7, if x_7 writes a letter, then x_7 is working, and that for all x_7, x_7 will not work we can infer that for all x_7, x_7 will not write a letter via universal modus tollens. Finally, from the fact that there is at least one x_7 for which x_7 will make tea if and only if x_7 will write a letter, and that for all x_7, x_7 will not write a letter we can infer that there is at least one x_7 for which x_7 will not make tea via existential biconditional elimination, which contradicts that For all x_7, x_7 will make tea. Therefore, the answer is no.