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 it snows, then Elisabeth is playing tennis. If it snows, then Elisabeth is playing tennis. If Elisabeth plays tennis, then it is snowing.
It is snowing if and only if Elisabeth is playing tennis can be inferred via the biconditional introduction rule. It is snowing if and only if Elisabeth is playing tennis can be inferred via the biconditional introduction rule. Elisabeth is playing tennis if and only if it is snowing can be inferred via the biconditional introduction rule. Elisabeth is playing tennis if and only if it is snowing can be inferred via the biconditional introduction rule.