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: It is not cloudy. It is cloudy if and only if David is a scientist. For all x_13, if x_13 were a scientist, then x_13 is drinking water. For all x_13, if x_13 drinks water, then x_13 is a scientist.
If it is cloudy, then David is a scientist can be inferred via the biconditional elimination rule. If David were a scientist, then it is cloudy can be inferred via the biconditional elimination rule. David is not a scientist can be inferred via the biconditional elimination rule. For all x_13, x_13 is a scientist if and only if x_13 will drink water can be inferred via the universal biconditional introduction rule. For all x_13, x_13 will drink water if and only if x_13 is a scientist can be inferred via the universal biconditional introduction rule.