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 Charles drinks water, then Elisabeth is fast. Elisabeth is fast if and only if Linda is a politician. If Elisabeth were fast, then Charles is drinking water. Charles is not drinking water.
Elisabeth is not fast can be inferred via the modus tollens rule. Charles is drinking water if and only if Elisabeth is fast can be inferred via the biconditional introduction rule. Elisabeth is fast if and only if Charles is drinking water can be inferred via the biconditional introduction rule. If Elisabeth were fast, then Linda is a politician can be inferred via the biconditional elimination rule. If Linda were a politician, then Elisabeth is fast can be inferred via the biconditional elimination rule.