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 will not play squash. For all x_6, x_6 will play squash or x_6 will not drink water. For all x_6, x_6 will drink water if and only if x_6 will write a letter.
For all x_6, if x_6 drinks water, then x_6 is playing squash can be inferred via the universal rewriting rule. For all x_6, if x_6 drinks water, then x_6 is writing a letter can be inferred via the universal biconditional elimination rule. For all x_6, if x_6 writes a letter, then x_6 is drinking water can be inferred via the universal biconditional elimination rule.