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_7, if x_7 takes a plane, then x_7 is a cashier. For all x_7, x_7 is a mechanic and x_7 will drive a car. There is at least one x_7 for which x_7 will take a plane.
There is at least one x_7 for which x_7 is a cashier can be inferred via the existential modus ponens rule. For all x_7, x_7 is a mechanic can be inferred via the universal simplification rule. For all x_7, x_7 will drive a car can be inferred via the universal simplification rule.