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_10, if x_10 writes a letter, then x_10 is drinking water. It is not late. David is drinking water if and only if it is late.
If David drinks water, then it is late can be inferred via the biconditional elimination rule. If it is late, then David is drinking water can be inferred via the biconditional elimination rule. David is not drinking water can be inferred via the biconditional elimination rule.