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: Susan is writing a letter if and only if it is windy. It is windy or Susan is not writing a letter.
If Susan writes a letter, then it is windy can be inferred via the rewriting rule. If Susan writes a letter, then it is windy can be inferred via the biconditional elimination rule. If it is windy, then Susan is writing a letter can be inferred via the biconditional elimination rule.