Consider the following premises. P_13(c) or ~Q_13(c). forall x_13: Q_13(x_13) -> P_13(x_13). forall x_13: P_13(x_13) -> Q_13(x_13). Can we infer Q_13(c) <-> P_13(c) from them?
 From forall x_13: P_13(x_13) -> Q_13(x_13), forall x_13: Q_13(x_13) -> P_13(x_13) we can infer forall x_13: P_13(x_13) <-> Q_13(x_13). From forall x_13: P_13(x_13) <-> Q_13(x_13) we can infer P_13(c) <-> Q_13(c). From P_13(c) or ~Q_13(c) we can infer Q_13(c) -> P_13(c). From P_13(c) <-> Q_13(c) we can infer P_13(c) -> Q_13(c). Finally, from Q_13(c) -> P_13(c), P_13(c) -> Q_13(c) we can infer Q_13(c) <-> P_13(c). Therefore, the answer is yes.