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_8, x_8 will play tennis if and only if x_8 is sad. For all x_8, x_8 is not sad. For all x_8, if x_8 were an office clerk, then x_8 is playing tennis. For all x_8, x_8 is an office clerk if and only if x_8 will drink water.
For all x_8, if x_8 plays tennis, then x_8 is sad can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 were an office clerk, then x_8 is drinking water can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 were sad, then x_8 is playing tennis can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 drinks water, then x_8 is an office clerk can be inferred via the universal biconditional elimination rule. For all x_8, x_8 will not play tennis can be inferred via the universal biconditional elimination rule.