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_8, x_8 will climb a mountain if and only if x_8 will play squash. There is at least one x_8 for which x_8 will make tea. For all x_8, if x_8 makes tea, then x_8 is playing squash.
There is at least one x_8 for which x_8 will play squash can be inferred via the existential modus ponens rule. For all x_8, if x_8 climbs a mountain, then x_8 is playing squash can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 plays squash, then x_8 is climbing a mountain can be inferred via the universal biconditional elimination rule.