Consider the following premises. It is overcast if and only if Charles is an electrician. Karen is a bartender if and only if it is overcast. Charles is an electrician or Karen is a bartender. Can we infer the following from them? If we can, name the inference rule being used: It is overcast.
 From the fact that Karen is a bartender if and only if it is overcast we can infer that if Karen were a bartender, then it is overcast via biconditional elimination. From the fact that it is overcast if and only if Charles is an electrician we can infer that if Charles were an electrician, then it is overcast via biconditional elimination. Finally, from the fact that if Charles were an electrician, then it is overcast, that if Karen were a bartender, then it is overcast, and that Charles is an electrician or Karen is a bartender we can infer that it is overcast via disjunction elimination. Therefore, the answer is yes.