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_23, if x_23 were a cashier, then x_23 is climbing a mountain. Robert is a cashier. For all x_23, if x_23 climbs a mountain, then x_23 is playing a game. For all x_23, if x_23 plays a game, then x_23 is climbing a mountain.
There is at least one x for which x is a cashier can be inferred via the existential generalization rule. For all x_23, if x_23 were a cashier, then x_23 is playing a game can be inferred via the universal transitivity rule. For all x_23, x_23 will climb a mountain if and only if x_23 will play a game can be inferred via the universal biconditional introduction rule. For all x_23, x_23 will play a game if and only if x_23 will climb a mountain can be inferred via the universal biconditional introduction rule.