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 x_12, if x_12 makes tea, then x_12 is a writer. James is not a writer. For all x_12, if x_12 were a writer, then x_12 is making tea.
For all x_12, x_12 will make tea if and only if x_12 is a writer can be inferred via the universal biconditional introduction rule. For all x_12, x_12 is a writer if and only if x_12 will make tea can be inferred via the universal biconditional introduction rule.