What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If it is late, then Robert is playing tennis. If Joseph were a janitor, then it is late. Joseph is a janitor or Robert is not playing tennis. Robert is not playing tennis.
It is not late. If Joseph were a janitor, then Robert is playing tennis. If Robert plays tennis, then Joseph is a janitor.