Consider the following premises. If it is late, then Jessica is drinking water. If Joseph were a janitor, then it is late. Joseph is a janitor if and only if Jessica is drinking water. Can we infer the following from them? If Joseph were a janitor, then Jessica is drinking water.
 From the fact that Joseph is a janitor if and only if Jessica is drinking water we can infer that if Jessica drinks water, then Joseph is a janitor. Finally, from the fact that if Joseph were a janitor, then it is late, and that if it is late, then Jessica is drinking water we can infer that if Joseph were a janitor, then Jessica is drinking water. Therefore, the answer is yes.