Consider the following premises. For all x_10, x_10 is not poor. Robert is a janitor. Robert is a janitor if and only if Mary is poor. Can we infer the following from them? Barbara is a carpenter.
 From the fact that Robert is a janitor we can infer that Robert is a janitor or Barbara is a carpenter. From the fact that for all x_10, x_10 is not poor we can infer that Mary is not poor. From the fact that Robert is a janitor if and only if Mary is poor, and that Mary is not poor we can infer that Robert is not a janitor. Finally, from the fact that Robert is a janitor or Barbara is a carpenter, and that Robert is not a janitor we can infer that Barbara is a carpenter. Therefore, the answer is yes. Notice, however, that the premises were contradictory, so we can infer anything from them.