Consider the following premises. It is raining if and only if Jennifer is a lawyer. If Charles were sad, then it is raining. For all x_15, if x_15 were a lawyer, then x_15 is a politician. Jennifer is not a politician. Can we infer the following from them? If we can, name the inference rule being used: Charles is not sad.
 From the fact that for all x_15, if x_15 were a lawyer, then x_15 is a politician we can infer that if Jennifer were a lawyer, then Jennifer is a politician via universal instantiation. From the fact that if Jennifer were a lawyer, then Jennifer is a politician, and that Jennifer is not a politician we can infer that Jennifer is not a lawyer via modus tollens. From the fact that it is raining if and only if Jennifer is a lawyer, and that Jennifer is not a lawyer we can infer that it is not raining via biconditional elimination. Finally, from the fact that if Charles were sad, then it is raining, and that it is not raining we can infer that Charles is not sad via modus tollens. Therefore, the answer is yes.