Consider the following premises. p. t_4 -> t_2. p -> t_4. Can we infer t_2 or r_4 from them? If possible, name the inference rules being used at each step.
 From p -> t_4, p we can infer t_4 via modus ponens. From t_4 -> t_2, t_4 we can infer t_2 via modus ponens. Finally, from t_2 we can infer t_2 or r_4 via addition. Therefore, the answer is yes.