Consider the following premises. If John were a lawyer, then John is making tea. It is late if and only if John is a lawyer. It is late or John is not making tea. Can we infer the following from them? It is late if and only if John is making tea.
 From the fact that it is late or John is not making tea we can infer that if John makes tea, then it is late. From the fact that it is late if and only if John is a lawyer we can infer that if it is late, then John is a lawyer. From the fact that if it is late, then John is a lawyer, and that if John were a lawyer, then John is making tea we can infer that if it is late, then John is making tea. Finally, from the fact that if it is late, then John is making tea, and that if John makes tea, then it is late we can infer that it is late if and only if John is making tea. Therefore, the answer is yes.