Consider the following premises. For all z, if z makes tea, then z is not playing a game. For all z, z will play a game. David is an electrician if and only if John is making tea. Can we infer the following from them? David is not an electrician.
 From the fact that for all z, if z makes tea, then z is not playing a game, and that for all z, z will play a game we can infer that for all z, z will not make tea. From the fact that for all z, z will not make tea we can infer that John is not making tea. From the fact that David is an electrician if and only if John is making tea we can infer that if David were an electrician, then John is making tea. Finally, from the fact that if David were an electrician, then John is making tea, and that John is not making tea we can infer that David is not an electrician. Therefore, the answer is yes.