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_6, x_6 is happy or x_6 will play tennis. For all x_6, x_6 is not happy. For all x_6, if x_6 plays tennis, then x_6 is a sailor. There is at least one x_6 for which if x_6 were a sailor, then x_6 is curious.
There is at least one x_6 for which if x_6 plays tennis, then x_6 is curious can be inferred via the existential transitivity rule. For all x_6, x_6 will play tennis can be inferred via the universal disjunctive syllogism rule.