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 will climb a mountain or x_8 is a politician. For all x_8, x_8 is an astronaut and x_8 will write a letter. For all x_8, x_8 will not climb a mountain.
There is at least one x_8 for which x_8 is a politician can be inferred via the existential disjunctive syllogism rule. For all x_8, x_8 is an astronaut can be inferred via the universal simplification rule. For all x_8, x_8 will write a letter can be inferred via the universal simplification rule.