What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If William plays a game, then Barbara is a sailor. If Barbara were a sailor, then William is playing a game. If Barbara were a sailor, then William is playing a game.
William is playing a game if and only if Barbara is a sailor. William is playing a game if and only if Barbara is a sailor. Barbara is a sailor if and only if William is playing a game. Barbara is a sailor if and only if William is playing a game.