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: There is at least one x_8 for which x_8 is not a cashier. For all x_8, x_8 will climb a mountain if and only if x_8 is a cashier. For all x_8, if x_8 were a cashier, then x_8 is playing squash. For all x_8, if x_8 plays squash, then x_8 is climbing a mountain.
For all x_8, if x_8 were a cashier, then x_8 is climbing a mountain can be inferred via the universal transitivity rule. For all x_8, if x_8 climbs a mountain, then x_8 is a cashier can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 were a cashier, then x_8 is climbing a mountain can be inferred via the universal biconditional elimination rule. There is at least one x_8 for which x_8 will not climb a mountain can be inferred via the existential biconditional elimination rule.