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_1 for which if x_1 takes a plane, then x_1 is happy. For all x_1, x_1 is not a scientist. For all x_1, if x_1 were happy, then x_1 is a scientist.
For all x_1, x_1 is not happy can be inferred via the universal modus tollens rule. There is at least one x_1 for which if x_1 takes a plane, then x_1 is a scientist can be inferred via the existential transitivity rule.