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, x_7 is an astronaut if and only if x_7 will play tennis. For all x_7, x_7 is a lawyer if and only if x_7 is a soldier. For all x_7, x_7 is not an astronaut. For all x_7, if x_7 were a lawyer, then x_7 is playing tennis.
For all x_7, if x_7 were an astronaut, then x_7 is playing tennis can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were a lawyer, then x_7 is a soldier can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 plays tennis, then x_7 is an astronaut can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were a soldier, then x_7 is a lawyer can be inferred via the universal biconditional elimination rule. For all x_7, x_7 will not play tennis can be inferred via the universal biconditional elimination rule.