Consider the following premises. There is at least one y_3 for which if y_3 were a janitor, then y_3 is making tea. For all y_3, if y_3 makes tea, then y_3 is a janitor. For all y_3, if y_3 makes tea, then y_3 is a janitor. Can we infer the following from them? For all y_3, if is not true that y_3 is a janitor if and only if y_3 will make tea.
 From the fact that there is at least one y_3 for which if y_3 were a janitor, then y_3 is making tea, and that for all y_3, if y_3 makes tea, then y_3 is a janitor we can infer that there is at least one y_3 for which y_3 is a janitor if and only if y_3 will make tea. From the fact that there is at least one y_3 for which y_3 is a janitor if and only if y_3 will make tea we can infer that there is at least one y_3 for which if y_3 were a janitor, then y_3 is making tea. Finally, from the fact that there is at least one y_3 for which if y_3 were a janitor, then y_3 is making tea, and that for all y_3, if y_3 makes tea, then y_3 is a janitor we can infer that there is at least one y_3 for which y_3 is a janitor if and only if y_3 will make tea, which contradicts that For all y_3, if is not true that y_3 is a janitor if and only if y_3 will make tea. Therefore, the answer is no.