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_5, if x_5 were curious, then x_5 is taking a plane. For all x_5, if x_5 were curious, then x_5 is not a doctor. For all x_5, if x_5 takes a plane, then x_5 is curious. For all x_5, x_5 is a doctor.
For all x_5, x_5 is not curious can be inferred via the universal modus tollens rule. For all x_5, x_5 is curious if and only if x_5 will take a plane can be inferred via the universal biconditional introduction rule. For all x_5, x_5 will take a plane if and only if x_5 is curious can be inferred via the universal biconditional introduction rule.