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 cold. It is late if and only if David is a taxi driver. For all y, y is not a taxi driver.
If it is late, then David is a taxi driver can be inferred via the biconditional elimination rule. If David were a taxi driver, then it is late can be inferred via the biconditional elimination rule.