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: exists y_2: R_1(y_2) -> R_3(y_2). forall y_2: R_3(y_2) -> R_1(y_2). forall y_2: ~R_3(y_2). forall y_2: R_1(y_2) -> R_3(y_2).
forall y_2: ~R_1(y_2) can be inferred via the universal modus tollens rule. exists y_2: ~R_1(y_2) can be inferred via the existential modus tollens rule. forall y_2: R_3(y_2) <-> R_1(y_2) can be inferred via the universal biconditional introduction rule. forall y_2: R_1(y_2) <-> R_3(y_2) can be inferred via the universal biconditional introduction rule. exists y_2: R_1(y_2) <-> R_3(y_2) can be inferred via the existential biconditional introduction rule. exists y_2: R_3(y_2) <-> R_1(y_2) can be inferred via the existential biconditional introduction rule.