Consider the following premises. q_1 <-> r_3. ~q_1. s -> r_3. Can we infer ~s from them? If possible, name the inference rules being used at each step.
 From q_1 <-> r_3, ~q_1 we can infer ~r_3 via biconditional elimination. Finally, from s -> r_3, ~r_3 we can infer ~s via modus tollens. Therefore, the answer is yes.