Consider the following premises. It is not sunny. It is cloudy. Charles is an electrician if and only if it is sunny. For all x_18, x_18 is a lawyer if and only if x_18 is an electrician. Can we infer the following from them? Charles is not a lawyer.
 From the fact that for all x_18, x_18 is a lawyer if and only if x_18 is an electrician we can infer that Charles is a lawyer if and only if Charles is an electrician. From the fact that Charles is an electrician if and only if it is sunny, and that it is not sunny we can infer that Charles is not an electrician. Finally, from the fact that Charles is a lawyer if and only if Charles is an electrician, and that Charles is not an electrician we can infer that Charles is not a lawyer. Therefore, the answer is yes.