Identify the type of irony in the following example:
A mean old man ate a large meal at a restaurant. The waitress tried to provide him with excellent service, but every time she brought him a dish, he complained. First he thought that the soup was too cold when it was hot. Then he said that his chicken steak was dry and chewy, when it was moist and succulent. Then he complained that one of her brown hairs was in his mashed potatoes, but the hair was actually grey like his own. She remained patient and continued to try to help him until the end of the meal, when he left her a a rupee for a tip. She replied on his way out, "Thank you for the generous tip, Mister."