Answer: The amusement park are
not liable to Dave injury, because Dave have already signed a memorandum of understanding with the amusement park, this shows that Dave already knows the injury he may get from riding the mechanical bull, but still decide to ride it.
What Dave signed was a warning from the the park, to their customers who wants to ride the mechanical bull, but still Dave did not want to listen to that warning. He has not ride the mechanical bull before, he could have asked for directions on how to control the bull.
The park will also have to show concerns on Dave's injury because it is an accident that happened to a customer in they park. A public liability insurance which covers third party injury should cover the life's of their customers who are within the parks premises.