Consider the following premises. t. q_2. p_1 <-> r_1. p_1 -> ~q_2. Can we infer r_1 from them? If possible, name the inference rules being used at each step.
 From p_1 -> ~q_2, q_2 we can infer ~p_1 via modus tollens. Finally, from p_1 <-> r_1, ~p_1 we can infer ~r_1 via biconditional elimination, which contradicts r_1. Therefore, the answer is no.