sphere capacitor with folded dielectric

$E (r) = \frac{Q}{4 \pi \epsilon_0 \epsilon_r} \frac{1}{r^2}$

$C = \frac{4 \pi \epsilon_0}{\frac{\frac{1}{r_1} - \frac{1}{r_2}}{\epsilon_{r 1}} + \frac{\frac{1}{r_2} - \frac{1}{r_3}}{\epsilon_{r 2}} + \frac{\frac{1}{r_3} - \frac{1}{r_4}}{\epsilon_{r 3}}}$