The graph shows the area y (in square feet) of rectangles that have a perimeter of 200 feet and a length of x feet.

a. Interpret the meaning of the vertex in this situation.
b. Write an equation for the parabola to predict the area of the rectangle when the length is 2 feet.
c. Compare the average rates of change in the area from 0 to 50 feet and 50 to 100 feet.