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: For all y_2, y_2 will not make tea. For all y_2, if y_2 makes tea, then y_2 is fast. There is at least one y_2 for which if y_2 makes tea, then y_2 is fast. For all y_2, if y_2 were fast, then y_2 is making tea.
For all y_2, y_2 is not fast can be inferred via the universal modus tollens rule. For all y_2, y_2 will make tea if and only if y_2 is fast can be inferred via the universal biconditional introduction rule. For all y_2, y_2 is fast if and only if y_2 will make tea can be inferred via the universal biconditional introduction rule. There is at least one y_2 for which y_2 will make tea if and only if y_2 is fast can be inferred via the existential biconditional introduction rule. There is at least one y_2 for which y_2 is fast if and only if y_2 will make tea can be inferred via the existential biconditional introduction rule.