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 climbs a mountain, then x_9 is making tea. There is at least one x_9 for which x_9 will not read a book. For all x_9, x_9 will read a book if and only if x_9 will take a plane. For all x_9, if x_9 makes tea, then x_9 is taking a plane.
For all x_9, if x_9 climbs a mountain, then x_9 is taking a plane can be inferred via the universal transitivity rule. For all x_9, if x_9 reads a book, then x_9 is taking a plane can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 takes a plane, then x_9 is reading a book can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which x_9 will not take a plane can be inferred via the existential biconditional elimination rule.