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_12, if x_12 takes a plane, then x_12 is curious. For all x_12, if x_12 takes a plane, then x_12 is a soldier. There is at least one x_12 for which if x_12 were curious, then x_12 is taking a plane. For all x_12, if x_12 were a soldier, then x_12 is taking a plane. For all x_12, x_12 is a soldier or x_12 is curious.
For all x_12, if x_12 were a soldier, then x_12 is curious can be inferred via the universal transitivity rule. There is at least one x_12 for which if x_12 were curious, then x_12 is a soldier can be inferred via the existential transitivity rule. There is at least one x_12 for which x_12 will take a plane can be inferred via the existential disjunction elimination rule. For all x_12, x_12 will take a plane if and only if x_12 is a soldier can be inferred via the universal biconditional introduction rule. For all x_12, x_12 is a soldier if and only if x_12 will take a plane can be inferred via the universal biconditional introduction rule. There is at least one x_12 for which x_12 is curious if and only if x_12 will take a plane can be inferred via the existential biconditional introduction rule. There is at least one x_12 for which x_12 will take a plane if and only if x_12 is curious can be inferred via the existential biconditional introduction rule.