100p
-20, 20, -10

S2 = S0 * r * r'

r(0.8, 0.8) = 100 * 0.8 * 0.8 = 64
r(0.8, 1.2) = 100 * 0.8 * 1.2 = 96
r(0.8, 0.9) = 100 * 0.8 * 0.9 = 72

r(1.2, 0.8) = 100 * 1.2 * 0.8 = 96
r(1.2, 1.2) = 100 * 1.2 * 1.2 = 144
r(1.2, 0.9) = 100 * 1.2 * 0.9 = 108

r(0.9, 0.8) = 100 * 0.9 * 0.8 = 72
r(0.9, 1.2) = 100 * 0.9 * 1.2 = 108
r(0.9, 0.9) = 100 * 0.9 * 0.9 = 81

1/3 * 1/3 = 1/9

varhato = 100 * 1/9 * (64 + 96 + 72 + 96 + 144 + 108 + 72 + 108 + 81) = 100/9 * 841 = 841/9