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, if x_9 were a politician, then x_9 is a doctor. For all x_9, if x_9 were a doctor, then x_9 is an electrician. For all x_9, if x_9 were a doctor, then x_9 is a politician. For all x_9, if x_9 were fast, then x_9 is a doctor. For all x_9, x_9 is a politician or x_9 is fast.
For all x_9, if x_9 were a politician, then x_9 is an electrician can be inferred via the universal transitivity rule. For all x_9, if x_9 were fast, then x_9 is an electrician can be inferred via the universal transitivity rule. For all x_9, if x_9 were fast, then x_9 is a politician can be inferred via the universal transitivity rule. For all x_9, x_9 is a doctor can be inferred via the universal disjunction elimination rule. For all x_9, x_9 is a politician if and only if x_9 is a doctor can be inferred via the universal biconditional introduction rule. For all x_9, x_9 is a doctor if and only if x_9 is a politician can be inferred via the universal biconditional introduction rule.