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_20, x_20 will play a game or x_20 will not climb a mountain. It is raining if and only if Sarah is climbing a mountain. For all x_20, x_20 will not play a game.
If it rains, then Sarah is climbing a mountain can be inferred via the biconditional elimination rule. If Sarah climbs a mountain, then it is raining can be inferred via the biconditional elimination rule. For all x_20, if x_20 climbs a mountain, then x_20 is playing a game can be inferred via the universal rewriting rule.