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_7, if x_7 takes a plane, then x_7 is playing tennis. For all x_7, x_7 will take a plane if and only if x_7 will play tennis.
For all x_7, if x_7 takes a plane, then x_7 is playing tennis can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 plays tennis, then x_7 is taking a plane can be inferred via the universal biconditional elimination rule.