Consider the following premises. If Robert were happy, then Robert is a doctor. If it rains, then Robert is happy. It is raining if and only if Robert is a doctor. Can we infer the following from them? If we can, name the inference rule being used: If it rains, then Robert is a doctor.
 From the fact that it is raining if and only if Robert is a doctor we can infer that if Robert were a doctor, then it is raining via biconditional elimination. Finally, from the fact that if it rains, then Robert is happy, and that if Robert were happy, then Robert is a doctor we can infer that if it rains, then Robert is a doctor via transitivity. Therefore, the answer is yes.