Consider the following premises. If it is late, then Robert is a poet. It is late or Robert is not a poet. If Robert were a poet, then David is not a scientist. David is a scientist. Can we infer the following from them? If we can, name the inference rule being used: It is not late.
 From the fact that it is late or Robert is not a poet we can infer that if Robert were a poet, then it is late via rewriting. From the fact that if Robert were a poet, then David is not a scientist, and that David is a scientist we can infer that Robert is not a poet via modus tollens. From the fact that if it is late, then Robert is a poet, and that if Robert were a poet, then it is late we can infer that it is late if and only if Robert is a poet via biconditional introduction. Finally, from the fact that it is late if and only if Robert is a poet, and that Robert is not a poet we can infer that it is not late via biconditional elimination. Therefore, the answer is yes.