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 John were fast, then it is sunny. It is raining if and only if it is sunny. If it is sunny, then John is fast. It is not raining.
John is fast if and only if it is sunny can be inferred via the biconditional introduction rule. It is sunny if and only if John is fast can be inferred via the biconditional introduction rule. If it rains, then it is sunny can be inferred via the biconditional elimination rule. If it is sunny, then it is raining can be inferred via the biconditional elimination rule. It is not sunny can be inferred via the biconditional elimination rule.