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_10, x_10 will write a letter. For all x_10, x_10 will climb a mountain or x_10 will read a book. For all x_10, if x_10 reads a book, then x_10 is a bartender. For all x_10, if x_10 takes a plane, then x_10 is a bartender. There is at least one x_10 for which if x_10 climbs a mountain, then x_10 is taking a plane.
There is at least one x_10 for which if x_10 climbs a mountain, then x_10 is a bartender can be inferred via the existential transitivity rule.