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: There is at least one x_9 for which x_9 is an astronaut if and only if x_9 will sleep. For all x_9, x_9 is an astronaut or x_9 is not a lawyer. For all x_9, x_9 will sleep or x_9 is a lawyer.
For all x_9, if x_9 were a lawyer, then x_9 is an astronaut can be inferred via the universal rewriting rule. There is at least one x_9 for which if x_9 were an astronaut, then x_9 is sleeping can be inferred via the existential biconditional elimination rule. There is at least one x_9 for which if x_9 sleeps, then x_9 is an astronaut can be inferred via the existential biconditional elimination rule.