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: If it snows, then John is reading a book. Michael is writing a letter if and only if John is reading a book. If Michael writes a letter, then it is snowing.
If Michael writes a letter, then John is reading a book can be inferred via the transitivity rule. If Michael writes a letter, then John is reading a book can be inferred via the biconditional elimination rule. If John reads a book, then Michael is writing a letter can be inferred via the biconditional elimination rule.