Consider the following premises. S_6(a_6) -> r. forall x_6: R_6(x_6) or S_6(x_6). t_4 -> r. ~R_6(a_6) or t_4. Can we infer t_4 -> r from them? If possible, name the inference rules being used at each step.
That is one of the premises. Therefore, the answer is yes.