Consider the following premises. U_2(a_5) -> Q_4(a_5). forall x_6: Q_4(x_6) -> Q_6(x_6). forall x_6: Q_6(x_6) -> U_2(x_6). Can we infer U_2(a_5) <-> Q_4(a_5) from them? If possible, name the inference rules being used at each step.
 From forall x_6: Q_4(x_6) -> Q_6(x_6), forall x_6: Q_6(x_6) -> U_2(x_6) we can infer forall x_6: Q_4(x_6) -> U_2(x_6) via universal transitivity. From forall x_6: Q_4(x_6) -> U_2(x_6) we can infer Q_4(a_5) -> U_2(a_5) via universal instantiation. Finally, from U_2(a_5) -> Q_4(a_5), Q_4(a_5) -> U_2(a_5) we can infer U_2(a_5) <-> Q_4(a_5) via biconditional introduction. Therefore, the answer is yes.