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_10, if x_10 were happy, then x_10 is fast. There is at least one x_10 for which if x_10 plays tennis, then x_10 is fast. For all x_10, x_10 is an astronaut. For all x_10, x_10 is happy or x_10 will play tennis.
There is at least one x_10 for which x_10 is fast can be inferred via the existential disjunction elimination rule.