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_1, if x_1 takes a plane, then x_1 is a police officer. There is at least one x_1 for which x_1 is sad. For all x_1, if x_1 were sad, then x_1 is taking a plane.
There is at least one x_1 for which x_1 will take a plane can be inferred via the existential modus ponens rule. For all x_1, if x_1 were sad, then x_1 is a police officer can be inferred via the universal transitivity rule.