Consider the following premises. For all x_19, x_19 is not an electrician. David is not making tea or William is writing a letter. Sarah is an electrician if and only if Richard is playing a game. David is making tea or Richard is playing a game. Can we infer the following from them? If we can, name the inference rule being used: William is not writing a letter.
 From the fact that David is making tea or Richard is playing a game, and that David is not making tea or William is writing a letter we can infer that Richard is playing a game or William is writing a letter via resolution. From the fact that for all x_19, x_19 is not an electrician we can infer that Sarah is not an electrician via universal instantiation. From the fact that Sarah is an electrician if and only if Richard is playing a game, and that Sarah is not an electrician we can infer that Richard is not playing a game via biconditional elimination. Finally, from the fact that Richard is playing a game or William is writing a letter, and that Richard is not playing a game we can infer that William is writing a letter via disjunctive syllogism, which contradicts that William is not writing a letter. Therefore, the answer is no.