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 poor. There is at least one x_4 for which x_4 is not poor or x_4 is a mechanic. For all x_4, if x_4 were an artist, then x_4 is playing squash. For all x_4, if x_4 were a mechanic, then x_4 is playing squash.
Nothing can be inferred from these premises.