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 Jennifer writes a letter, then it is not snowing. It is sunny if and only if Jennifer is writing a letter. It is snowing.
Jennifer is not writing a letter can be inferred via the modus tollens rule. If it is sunny, then Jennifer is writing a letter can be inferred via the biconditional elimination rule. If Jennifer writes a letter, then it is sunny can be inferred via the biconditional elimination rule.