+170 The figure below shows the ellipse \($\frac{(x-20)^2}{20}+\frac{(y-16)^2}{16}=2016$\). Let R_1,R_2,R_3, and R_4 denote those areas within the ellipse that are in the first, second, third, and fourth quadrants, respectively. Determine the value of $R_1-R_2+R_3-R_4$.
