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: For all x, if x were a taxi driver, then x is playing a game. For all x, x is not a taxi driver. For all x, x will play a game if and only if x is a taxi driver. For all x, if x were sad, then x is playing a game.
For all x, if x plays a game, then x is a taxi driver can be inferred via the universal biconditional elimination rule. For all x, if x were a taxi driver, then x is playing a game can be inferred via the universal biconditional elimination rule. For all x, x will not play a game can be inferred via the universal biconditional elimination rule.