What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Michael is sad or it is not snowing. Robert is not a writer. If Michael were sad, then it is snowing. Robert is a writer if and only if Michael is sad.
If it snows, then Michael is sad. If Robert were a writer, then Michael is sad. If Michael were sad, then Robert is a writer. Michael is not sad.