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_6, x_6 is happy or x_6 will not play tennis. There is at least one x_6 for which x_6 will play tennis or x_6 is a bartender. For all x_6, x_6 is a bartender if and only if x_6 is happy.
For all x_6, if x_6 plays tennis, then x_6 is happy can be inferred via the universal rewriting rule. For all x_6, if x_6 were a bartender, then x_6 is happy can be inferred via the universal biconditional elimination rule. For all x_6, if x_6 were happy, then x_6 is a bartender can be inferred via the universal biconditional elimination rule.