Consider the following premises. p_4 <-> q. p -> p_4. p or q. Can we infer p_4 from them? If possible, name the inference rules being used at each step.
 From p_4 <-> q we can infer q -> p_4 via biconditional elimination. Finally, from p -> p_4, q -> p_4, p or q we can infer p_4 via disjunction elimination. Therefore, the answer is yes.