Hard geometry problem, help!

Let R be the circle centered at (0,0) with radius 10. The lines x = 6 and y = 4 divide R into four regions R₁, R₂, R₃, and R₄. Let [R_i] denote the area of region R_i. If

[R₁] > [R₂] > [R₃] > [R₄],

then find [R₁] - [R₂] - [R₃] + [R₄]