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 William were rich, then it is overcast. It is overcast if and only if William is playing a game. William is not playing a game. For all x_17, if x_17 plays a game, then x_17 is rich.
If it is overcast, then William is playing a game can be inferred via the biconditional elimination rule. If William plays a game, then it is overcast can be inferred via the biconditional elimination rule.