Consider the following premises. ~w_1. p_3 <-> w_1. Can we infer ~p_3 or u_2 from them? If possible, name the inference rules being used at each step.
 From p_3 <-> w_1, ~w_1 we can infer ~p_3 via biconditional elimination. Finally, from ~p_3 we can infer ~p_3 or u_2 via addition. Therefore, the answer is yes.