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_4, x_4 is a mechanic or x_4 will cook. For all x_4, if x_4 cooks, then x_4 is an astronaut. For all x_4, if x_4 were a mechanic, then x_4 is an astronaut.
For all x_4, x_4 is an astronaut can be inferred via the universal disjunction elimination rule.