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_13 for which if x_13 were a janitor, then x_13 is a cashier. For all x_13, if x_13 were an astronaut, then x_13 is a janitor. For all x_13, x_13 will listen to a song. For all x_13, if x_13 takes a plane, then x_13 is a janitor. For all x_13, x_13 will take a plane or x_13 is an astronaut.
There is at least one x_13 for which if x_13 were an astronaut, then x_13 is a cashier can be inferred via the existential transitivity rule. There is at least one x_13 for which if x_13 takes a plane, then x_13 is a cashier can be inferred via the existential transitivity rule. For all x_13, x_13 is a janitor can be inferred via the universal disjunction elimination rule.