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_9, x_9 will drink water if and only if x_9 will play squash. Mary is not drinking water.
For all x_9, if x_9 drinks water, then x_9 is playing squash can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 plays squash, then x_9 is drinking water can be inferred via the universal biconditional elimination rule.