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 is happy or x_15 will not drive a car. For all x_15, x_15 will cook or x_15 will drive a car. For all x_15, if x_15 cooks, then x_15 is happy. For all x_15, x_15 is not a cashier. There is at least one x_15 for which x_15 is a cashier or x_15 is a mechanic.
There is at least one x_15 for which x_15 is a mechanic can be inferred via the existential disjunctive syllogism rule. For all x_15, if x_15 drives a car, then x_15 is happy can be inferred via the universal rewriting rule.