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 snowing or Robert is not a server. William is fast or Robert is a server. William is fast if and only if it is snowing.
If Robert were a server, then it is snowing can be inferred via the rewriting rule. If William were fast, then it is snowing can be inferred via the biconditional elimination rule. If it snows, then William is fast can be inferred via the biconditional elimination rule.