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_15, x_15 will read a book or x_15 is a janitor. For all x_15, if x_15 were bored, then x_15 is not a cashier. There is at least one x_15 for which if x_15 reads a book, then x_15 is a cashier. For all x_15, if x_15 drinks water, then x_15 is bored. For all x_15, if x_15 were a janitor, then x_15 is a cashier.
There is at least one x_15 for which x_15 is a cashier can be inferred via the existential disjunction elimination rule.