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: Robert is listening to a song or John is a writer. If it is windy, then it is late. If Robert listens to a song, then it is windy. John is a writer if and only if it is windy.
If Robert listens to a song, then it is late can be inferred via the transitivity rule. If John were a writer, then it is windy can be inferred via the biconditional elimination rule. If it is windy, then John is a writer can be inferred via the biconditional elimination rule.