If my math is correct B or C is what it comes down to
This type of parabola opens either to the left or to the right. The negative makes it open to the left.
Since ur using r as a variable the answer is r = 7.
Find the area of the blue square including the white square then find the area of the white square and subtract that from the area of the blue square.
Hope that helps if you need more help just comment and I’ll try to explain it better!