What is the exposition for "Life as we Knew It"?I have all of the rest of the plot, I just need help on this one part.

I think the exposition would just be the beginning part where we first learn that there is going to be an asteroid hitting the moon.  When all the teachers at school assign moon projects and papers, etc., it tells us that the moon thing is going to be important to the rest of the story, and builds excitement over the event. 

When the crater hits and the moon's position is altered, the rising action begins.