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_23 for which x_23 is rich if and only if x_23 is happy. For all x_23, x_23 will climb a mountain if and only if x_23 is a server. For all x_23, x_23 is not happy. For all x_23, x_23 will climb a mountain if and only if x_23 is rich. For all x_23, if x_23 works, then x_23 is a server.
For all x_23, if x_23 climbs a mountain, then x_23 is a server can be inferred via the universal biconditional elimination rule. For all x_23, if x_23 climbs a mountain, then x_23 is rich can be inferred via the universal biconditional elimination rule. There is at least one x_23 for which if x_23 were rich, then x_23 is happy can be inferred via the existential biconditional elimination rule. For all x_23, if x_23 were a server, then x_23 is climbing a mountain can be inferred via the universal biconditional elimination rule. For all x_23, if x_23 were rich, then x_23 is climbing a mountain can be inferred via the universal biconditional elimination rule. There is at least one x_23 for which if x_23 were happy, then x_23 is rich can be inferred via the existential biconditional elimination rule. There is at least one x_23 for which x_23 is not rich can be inferred via the existential biconditional elimination rule.