Consider the following premises. For all x_5, x_5 is a janitor if and only if x_5 will make tea. For all x_5, if x_5 were a janitor, then x_5 is a mechanic. For all x_5, x_5 is not a mechanic. Can we infer the following from them? There is at least one x_5 for which x_5 will make tea.
 From the fact that for all x_5, if x_5 were a janitor, then x_5 is a mechanic, and that for all x_5, x_5 is not a mechanic we can infer that for all x_5, x_5 is not a janitor. From the fact that for all x_5, x_5 is a janitor if and only if x_5 will make tea we can infer that for all x_5, if x_5 makes tea, then x_5 is a janitor. Finally, from the fact that for all x_5, if x_5 makes tea, then x_5 is a janitor, and that for all x_5, x_5 is not a janitor we can infer that for all x_5, x_5 will not make tea, which contradicts that There is at least one x_5 for which x_5 will make tea. Therefore, the answer is no.