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_5 for which if x_5 were a soldier, then x_5 is a cashier. For all x_5, x_5 will take a plane. For all x_5, x_5 is a cashier if and only if x_5 will take a plane.
For all x_5, if x_5 were a cashier, then x_5 is taking a plane can be inferred via the universal biconditional elimination rule. For all x_5, if x_5 takes a plane, then x_5 is a cashier can be inferred via the universal biconditional elimination rule.