My swimming pool contractor presented me with a bill for a rock clause in excavating a swimming pool at our house. It was only at that time (first time) that he informed me his subcontractor billed at $1,350 an hour. When I expressed surprise, he said, you agreed that this rock clause cost would be extra. Did he (contractor) have an obligation to inform me of the hourly rate and get my approval before the work was done? Thank you.