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_2 for which x_2 will take a plane if and only if x_2 is a server. For all x_2, x_2 is a server if and only if x_2 will take a plane.
For all x_2, if x_2 were a server, then x_2 is taking a plane can be inferred via the universal biconditional elimination rule. There is at least one x_2 for which if x_2 takes a plane, then x_2 is a server can be inferred via the existential biconditional elimination rule. For all x_2, if x_2 takes a plane, then x_2 is a server can be inferred via the universal biconditional elimination rule. There is at least one x_2 for which if x_2 were a server, then x_2 is taking a plane can be inferred via the existential biconditional elimination rule.