Consider the following premises. If it is not overcast, then it is late. Charles is an electrician if and only if it is sunny. It is overcast if and only if it is sunny. Charles is not an electrician. Can we infer the following from them? If we can, name the inference rule being used: It is not late.
 From the fact that Charles is an electrician if and only if it is sunny, and that Charles is not an electrician we can infer that it is not sunny via biconditional elimination. From the fact that it is overcast if and only if it is sunny, and that it is not sunny we can infer that it is not overcast via biconditional elimination. Finally, from the fact that if it is not overcast, then it is late, and that it is not overcast we can infer that it is late via modus ponens, which contradicts that It is not late. Therefore, the answer is no.