Let R be the circle centered at (0,0) with radius 10. The lines x = 6 and y = 5 divide R into four regions R1, R2, R3, and R4. Let [Ri] denote the area of region Ri. If [R1] > [R2] > [R3] > [R4], then find [R1]-[R2]-[R3]+[R4].
[R1] - [R2] - [R3] + [R4] = 140.
