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_9, x_9 is a poet or x_9 is an astronaut. For all x_9, x_9 is not a scientist. For all x_9, x_9 is a poet if and only if x_9 is poor. For all x_9, if x_9 were poor, then x_9 is a scientist.
For all x_9, x_9 is not poor can be inferred via the universal modus tollens rule. For all x_9, if x_9 were a poet, then x_9 is poor can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 were poor, then x_9 is a poet can be inferred via the universal biconditional elimination rule.