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: It is windy if and only if Mary is not writing a letter. It is not raining. Mary is writing a letter if and only if it is raining.
If it is windy, then Mary is not writing a letter can be inferred via the biconditional elimination rule. If Mary writes a letter, then it is raining can be inferred via the biconditional elimination rule. If Mary doesn't write a letter, then it is windy can be inferred via the biconditional elimination rule. If it rains, then Mary is writing a letter can be inferred via the biconditional elimination rule. Mary is not writing a letter can be inferred via the biconditional elimination rule.