Consider the following premises. forall x_18: P_18(x_18). forall x_9: P_9(x_9). Can we infer P_18(a_18) and P_9(i) from them? If possible, name the inference rules being used at each step.
 From forall x_18: P_18(x_18) we can infer P_18(a_18) via universal instantiation. From forall x_9: P_9(x_9) we can infer P_9(i) via universal instantiation. Finally, from P_18(a_18), P_9(i) we can infer P_18(a_18) and P_9(i) via conjunction. Therefore, the answer is yes.