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: Barbara is climbing a mountain or Elisabeth is a soldier. Barbara is climbing a mountain if and only if David is a server. David is a server or Elisabeth is not a soldier.
If Elisabeth were a soldier, then David is a server can be inferred via the rewriting rule. If Barbara climbs a mountain, then David is a server can be inferred via the biconditional elimination rule. If David were a server, then Barbara is climbing a mountain can be inferred via the biconditional elimination rule.