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_3, x_3 will not play squash. For all x_3, x_3 is sad. For all x_3, x_3 will play squash or x_3 is an astronaut.
For all x_3, x_3 is an astronaut can be inferred via the universal disjunctive syllogism rule.