What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: R(d) -> r_1. forall x_3: U_2(x_3) <-> R(x_3). u_2 -> U_2(d).
forall x_3: U_2(x_3) -> R(x_3) can be inferred via the universal biconditional elimination rule. forall x_3: R(x_3) -> U_2(x_3) can be inferred via the universal biconditional elimination rule.