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 for which x will climb a mountain or x is a cashier. For all x, if x were a cashier, then x is driving a car. For all x, if x climbs a mountain, then x is driving a car. For all x, if x drives a car, then x is climbing a mountain.
For all x, if x were a cashier, then x is climbing a mountain can be inferred via the universal transitivity rule. There is at least one x for which x will drive a car can be inferred via the existential disjunction elimination rule. For all x, x will climb a mountain if and only if x will drive a car can be inferred via the universal biconditional introduction rule. For all x, x will drive a car if and only if x will climb a mountain can be inferred via the universal biconditional introduction rule.