Oh man, I actually remember enough calculus to find the area of that section in the math problem at the beginning! As touma was starting to say, you find the intersection points by solving for the results of "f(x) = g(x)" (they look like basic parabolas which means the quadratic formula will be more than enough), and then to get the area, you take the integral over the difference of the functions from point a to point b (the intersection points you found).