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_18, x_18 is a carpenter if and only if x_18 will play squash. For all x_18, x_18 is a carpenter if and only if x_18 will drink water. Thomas is working if and only if Sarah is drinking water. For all x_18, x_18 will not play squash. Thomas is working or Joseph is writing a letter.
If Thomas works, then Sarah is drinking water can be inferred via the biconditional elimination rule. If Sarah drinks water, then Thomas is working can be inferred via the biconditional elimination rule. For all x_18, if x_18 were a carpenter, then x_18 is playing squash can be inferred via the universal biconditional elimination rule. For all x_18, if x_18 were a carpenter, then x_18 is drinking water can be inferred via the universal biconditional elimination rule. For all x_18, if x_18 plays squash, then x_18 is a carpenter can be inferred via the universal biconditional elimination rule. For all x_18, if x_18 drinks water, then x_18 is a carpenter can be inferred via the universal biconditional elimination rule. For all x_18, x_18 is not a carpenter can be inferred via the universal biconditional elimination rule.