What is the exposition in The River by Gary Paulsen?

Exposition is generally found at the beginning of any story. During the exposition, the author introduces the reader to the characters, setting, and central conflict. In The River, author Gary Paulsen's exposition extends through the first three chapters.Within these first three chapters, we meet Brian Robeson and learn he survived on his own while being stranded for nearly two months in the Canadian wilderness, a story Paulsen relays in the first book of the series, Hatchet. In the opening chapter, three men from what they call a "government survival school" come to Brian's home with a proposition. They believe Brian has a special gift that allowed him to become in tune with nature to the extent he did in order to survive. Since the men are teaching survival skills, they want Brian to, as they say, "do it again" so that they can learn from him, watch him think through the challenges he would face in order to survive a second time (p. 3). One of the men is the second central character in the second central character in the story, government psychologist Derek Holtzer.The central conflict is that neither Brian nor his parents really want him to go through the survival ordeal again. Yet, at the same time, Brian knows he grew so much from his experience and changed so much that he partially feels like he no longer fits in with his urban environment, especially because no one, not even his psychologist, can understand just how much he grew from the experience, how ultimately positive the experience was. Instead, everyone around him only sees his experience as traumatic. Brian feels driven to undertake the experience on more time to convince himself it truly was a beneficial experience and to teach others how to benefit from the same experience.
http://edtech2.boisestate.edu/weltys/502/conceptmap.html