Consider the following premises. s_4 -> w_4. q and r_4. q <-> s_4. Can we infer w_4 from them? If possible, name the inference rules being used at each step.
 From q <-> s_4 we can infer q -> s_4 via biconditional elimination. From q -> s_4, s_4 -> w_4 we can infer q -> w_4 via transitivity. From q and r_4 we can infer q via simplification. Finally, from q -> w_4, q we can infer w_4 via modus ponens. Therefore, the answer is yes.